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Precalculus 9e by MICHAEL SULLIVAN

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  • 1. “Things to A detailed list of important theorems, Review these and you’ll know the 340–341 Know” formulas,and definitions most important material in the chapter! from the chapter. “You Should Be Contains a complete list of objectives by Do the recommended exercises and 341–342 Able to…” section,examples that illustrate the you’ll have mastery over the key objective,and practice exercises that test material. If you get something wrong, your understanding of the objective. review the suggested page numbers and try again. Review These provide comprehensive review and Practice makes perfect.These problems 342–345 Exercises practice of key skills,matched to the combine exercises from all sections, Learning Objectives for each section. giving you a comprehensive review in one place. CHAPTER TEST About 15–20 problems that can be taken Be prepared. Take the sample practice 346 as a Chapter Test.Be sure to take the test under test conditions.This will Chapter Test under test conditions—no get you ready for your instructor’s test. notes! If you get a problem wrong,watch the Chapter Test Prep video. CUMULATIVE These problem sets appear at the end of These are really important. They will 346–347 REVIEW each chapter,beginning with Chapter 2. ensure that you are not forgetting They combine problems from previous anything as you go. These will go a long chapters,providing an ongoing way toward keeping you constantly cumulative review. primed for the final exam. CHAPTER The Chapter Project applies what you’ve The Project gives you an opportunity to 347–348 PROJECTS learned in the chapter.Additional projects apply what you’ve learned in the chapter are available on the Instructor’s to solve a problem related to the Resource Center (IRC). opening article. If your instructor allows, these make excellent opportunities to work in a group,which is often the best way of learning math. NEW! Internet-based In selected chapters,a web-based The projects allow the opportunity for 347–348 Projects project is given. students to collaborate and use mathematics to deal with issues that come up in their lives. Review “Study for Quizzes and Tests” Feature Description Benefit Page Chapter Reviews at the end of each chapter contain…
  • 2. As you begin, you may feel anxious about the number of theorems, definitions, procedures, and equations. You may wonder if you can learn it all in time. Don’t worry, your concerns are normal. This textbook was written with you in mind. If you attend class, work hard, and read and study this book, you will build the knowledge and skills you need to be successful. Here’s how you can use the book to your benefit. Read Carefully When you get busy, it’s easy to skip reading and go right to the problems. Don’t. . . the book has a large number of examples and clear explanations to help you break down the mathematics into easy-to-understand steps. Reading will provide you with a clearer understanding, beyond simple memorization. Read before class (not after) so you can ask questions about anything you didn’t understand.You’ll be amazed at how much more you’ll get out of class if you do this. Use the Features I use many different methods in the classroom to communicate. Those methods, when incorporated into the book, are called “features.” The features serve many purposes, from providing timely review of material you learned before (just when you need it), to providing organized review sessions to help you prepare for quizzes and tests.Take advantage of the features and you will master the material. To make this easier, I’ve provided a brief guide to getting the most from this book. Refer to the “Prepare for Class,”“Practice,” and “Review” pages on the inside front cover of this book. Spend fifteen minutes reviewing the guide and familiarizing yourself with the features by flipping to the page numbers provided. Then, as you read, use them.This is the best way to make the most of your textbook. Please do not hesitate to contact me, through Pearson Education, with any questions, suggestions, or comments that would improve this text. I look forward to hearing from you, and good luck with all of your studies. Best Wishes! Michael Sullivan To the Student
  • 3. To the Memory of My Mother and Father
  • 4. PRECALCULUS N I N T H E D I T I O N
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  • 6. Prentice Hall PRECALCULUS N I N T H E D I T I O N Michael Sullivan Chicago State University Boston Columbus Indianapolis New York San Francisco Upper Saddle River Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo
  • 7. Editor in Chief: Anne Kelly Sponsoring Editor: Dawn Murrin Assistant Editor: Joseph Colella Marketing Manager: Peggy Lucas Senior Managing Editor: Karen Wernholm Associate Managing Editor: Tamela Ambush Senior Production Project Manager: Peggy McMahon Production Editor: Sherry Berg, Nesbitt Graphics, Inc. Senior Design Supervisor: Andrea Nix Art Direction and Cover Design: Barbara T.Atkinson Interior Design: Tamara Newnam Image Manager/Image Management Services: Rachel Youdelman Photo Researcher: Caroline Commins Permissions Project Supervisor: Michael Joyce Media Producer: Vicki Dreyfus Senior Author Support/Technology Specialist: Joe Vetere Manufacturing Manager: Evelyn Beaton Senior Manufacturing Buyer: Carol Melville Composition: MPS Limited, a Macmillan Company Technical Illustrations: Precision Graphics and Laserwords Printer/Binder: Courier/Kendallville Cover Printer: Lehigh-Phoenix Color/Hagerstown Text Font: Times Ten Roman Credits and acknowledgments borrowed from other sources and reproduced, with permission, in this textbook appear on page xxx. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks.Where those designations appear in this book, and Pearson was aware of a trademark claim, the designations have been printed in initial caps or all caps. Library of Congress Cataloging-in-Publication Data Sullivan, Michael, 1942– Precalculus / Michael Sullivan.—9th ed. p. cm. ISBN-13: 978-0-321-71683-5 ISBN-10: 0-321-71683-3 1.Algebra—Textbooks. 2. Trigonometry—Textbooks. I.Title. QA154.3.S85 2012 512—dc22 2010050954 Copyright © 2012, 2008, 2005, and 2002 by Pearson Education, Inc.All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. For information on obtaining permission for use of material in this work, please submit a written request to Pearson Education, Inc., Rights and Contracts Department, 501 Boylston Street, Suite 900, Boston, MA 02116, fax your request to 617-671-3447, or e-mail at http://www.pearsoned.com/legal/permissions.htm. 1 2 3 4 5 6 7 8 9 10—CRK—15 14 13 12 11 ISBN-10: 0-321-71683-3 ISBN-13: 978-0-321-71683-5
  • 8. To the Student ii Preface to the Instructor xvi Applications Index xxiii Photo Credits xxx 1 Graphs 1 1.1 The Distance and Midpoint Formulas 2 1.2 Graphs of Equations in Two Variables; Intercepts; Symmetry 9 1.3 Lines 19 1.4 Circles 34 Chapter Review 41 Chapter Test 43 Chapter Project 43 2 Functions and Their Graphs 45 2.1 Functions 46 2.2 The Graph of a Function 60 2.3 Properties of Functions 68 2.4 Library of Functions; Piecewise-defined Functions 80 2.5 Graphing Techniques:Transformations 90 2.6 Mathematical Models: Building Functions 103 Chapter Review 109 Chapter Test 114 Cumulative Review 115 Chapter Projects 115 3 Linear and Quadratic Functions 117 3.1 Linear Functions and Their Properties 118 3.2 Linear Models: Building Linear Functions from Data 128 3.3 Quadratic Functions and Their Properties 134 3.4 Build Quadratic Models from Verbal Descriptions and from Data 146 3.5 Inequalities Involving Quadratic Functions 155 Chapter Review 159 Chapter Test 162 Cumulative Review 163 Chapter Projects 164 Table of Contents ix
  • 9. 4 Polynomial and Rational Functions 165 4.1 Polynomial Functions and Models 166 4.2 Properties of Rational Functions 188 4.3 The Graph of a Rational Function 199 4.4 Polynomial and Rational Inequalities 214 4.5 The Real Zeros of a Polynomial Function 220 4.6 Complex Zeros; Fundamental Theorem of Algebra 233 Chapter Review 239 Chapter Test 243 Cumulative Review 243 Chapter Projects 244 5 Exponential and Logarithmic Functions 246 5.1 Composite Functions 247 5.2 One-to-One Functions; Inverse Functions 254 5.3 Exponential Functions 267 5.4 Logarithmic Functions 283 5.5 Properties of Logarithms 296 5.6 Logarithmic and Exponential Equations 305 5.7 Financial Models 312 5.8 Exponential Growth and Decay Models; Newton’s Law; Logistic Growth and Decay Models 322 5.9 Building Exponential, Logarithmic, and Logistic Models from Data 332 Chapter Review 340 Chapter Test 346 Cumulative Review 346 Chapter Projects 347 6 Trigonometric Functions 349 6.1 Angles and Their Measure 350 6.2 Trigonometric Functions: Unit Circle Approach 363 6.3 Properties of the Trigonometric Functions 379 6.4 Graphs of the Sine and Cosine Functions 393 6.5 Graphs of the Tangent, Cotangent, Cosecant, and Secant Functions 408 6.6 Phase Shift; Sinusoidal Curve Fitting 415 Chapter Review 426 Chapter Test 432 Cumulative Review 433 Chapter Projects 434 x Table of Contents
  • 10. 7 Analytic Trigonometry 435 7.1 The Inverse Sine, Cosine, and Tangent Functions 436 7.2 The Inverse Trigonometric Functions (Continued) 448 7.3 Trigonometric Equations 454 7.4 Trigonometric Identities 464 7.5 Sum and Difference Formulas 472 7.6 Double-angle and Half-angle Formulas 484 7.7 Product-to-Sum and Sum-to-Product Formulas 494 Chapter Review 498 Chapter Test 502 Cumulative Review 502 Chapter Projects 503 8 Applications of Trigonometric Functions 504 8.1 Right Triangle Trigonometry;Applications 505 8.2 The Law of Sines 517 8.3 The Law of Cosines 528 8.4 Area of a Triangle 535 8.5 Simple Harmonic Motion; Damped Motion; Combining Waves 541 Chapter Review 550 Chapter Test 554 Cumulative Review 555 Chapter Projects 555 9 Polar Coordinates;Vectors 557 9.1 Polar Coordinates 558 9.2 Polar Equations and Graphs 567 9.3 The Complex Plane; De Moivre’s Theorem 582 9.4 Vectors 589 9.5 The Dot Product 603 9.6 Vectors in Space 610 9.7 The Cross Product 620 Chapter Review 625 Chapter Test 629 Cumulative Review 629 Chapter Projects 630 Table of Contents xi
  • 11. 10 Analytic Geometry 631 10.1 Conics 632 10.2 The Parabola 633 10.3 The Ellipse 642 10.4 The Hyperbola 652 10.5 Rotation of Axes; General Form of a Conic 665 10.6 Polar Equations of Conics 673 10.7 Plane Curves and Parametric Equations 678 Chapter Review 691 Chapter Test 694 Cumulative Review 694 Chapter Projects 695 11 Systems of Equations and Inequalities 696 11.1 Systems of Linear Equations: Substitution and Elimination 697 11.2 Systems of Linear Equations: Matrices 712 11.3 Systems of Linear Equations: Determinants 727 11.4 Matrix Algebra 736 11.5 Partial Fraction Decomposition 753 11.6 Systems of Nonlinear Equations 761 11.7 Systems of Inequalities 770 11.8 Linear Programming 777 Chapter Review 784 Chapter Test 789 Cumulative Review 790 Chapter Projects 790 12 Sequences; Induction; the Binomial Theorem 792 12.1 Sequences 793 12.2 Arithmetic Sequences 803 12.3 Geometric Sequences; Geometric Series 809 12.4 Mathematical Induction 820 12.5 The Binomial Theorem 824 Chapter Review 830 Chapter Test 833 Cumulative Review 833 Chapter Projects 834 xii Table of Contents
  • 12. Table of Contents xiii 13 Counting and Probability 835 13.1 Counting 836 13.2 Permutations and Combinations 841 13.3 Probability 850 Chapter Review 860 Chapter Test 862 Cumulative Review 863 Chapter Projects 863 14 A Preview of Calculus:The Limit, Derivative,and Integral of a Function 865 14.1 Finding Limits Using Tables and Graphs 866 14.2 Algebra Techniques for Finding Limits 871 14.3 One-sided Limits; Continuous Functions 878 14.4 The Tangent Problem;The Derivative 885 14.5 The Area Problem;The Integral 892 Chapter Review 898 Chapter Test 902 Chapter Projects 903 Appendix A Review A1 A.1 Algebra Essentials A1 A.2 Geometry Essentials A14 A.3 Polynomials A22 A.4 Synthetic Division A32 A.5 Rational Expressions A36 A.6 Solving Equations A44 A.7 Complex Numbers; Quadratic Equations in the Complex Number System A54 A.8 Problem Solving: Interest, Mixture, Uniform Motion, Constant Rate Job Applications A62 A.9 Interval Notation; Solving Inequalities A72 A.10 nth Roots; Rational Exponents A81
  • 13. xiv Table of Contents Appendix B Graphing Utilities B1 B.1 The Viewing Rectangle B1 B.2 Using a Graphing Utility to Graph Equations B3 B.3 Using a Graphing Utility to Locate Intercepts and Check for Symmetry B5 B.4 Using a Graphing Utility to Solve Equations B6 B.5 Square Screens B8 B.6 Using a Graphing Utility to Graph Inequalities B9 B.7 Using a Graphing Utility to Solve Systems of Linear Equations B9 B.8 Using a Graphing Utility to Graph a Polar Equation B11 B.9 Using a Graphing Utility to Graph Parametric Equations B11 Answers AN1 Index I1
  • 14. Students have different goals, learning styles, and levels of preparation. Instructors have different teaching philosophies, styles, and techniques. Rather than write one series to fit all, the Sullivans have written three distinct series. All share the same goal—to develop a high level of mathematical understanding and an appreciation for the way mathematics can describe the world around us.The manner of reaching that goal, however, differs from series to series. Contemporary Series,Ninth Edition The Contemporary Series is the most traditional in approach yet modern in its treatment of precalculus mathematics. Graphing utility coverage is optional and can be included or excluded at the discretion of the instructor: College Algebra,Algebra & Trigonometry,Trigonometry, Precalculus. Enhanced with Graphing Utilities Series, Fifth Edition This series provides a more thorough integration of graphing utilities into topics, allowing students to explore mathematical concepts and foreshadow ideas usually studied in later courses. Using technology, the approach to solving certain problems differs from the Contemporary Series, while the emphasis on understanding concepts and building strong skills does not: College Algebra, Algebra & Trigonometry, Trigonometry, Precalculus. Concepts through Functions Series, Second Edition This series differs from the others, utilizing a functions approach that serves as the organizing principle tying concepts together. Functions are introduced early in various formats. This approach supports the Rule of Four, which states that functions are represented symbolically, numerically, graphically, and verbally. Each chapter introduces a new type of function and then develops all concepts pertaining to that particular function. The solutions of equations and inequalities, instead of being developed as stand-alone topics, are developed in the context of the underlying functions. Graphing utility coverage is optional and can be included or excluded at the discretion of the instructor: College Algebra; Precalculus, with a Unit Circle Approach to Trigonometry; Precalculus, with a Right Triangle Approach to Trigonometry. xv Three Distinct Series
  • 15. xvi A s a professor of mathematics at an urban public university for 35 years, I understand the varied needs of students taking precalculus. Students range from being underprepared, with little mathematical background and a fear of mathematics, to being highly prepared and motivated.For some,this is their final course in mathematics. For others, it is preparation for future mathematics courses. I have written this text with both groups in mind. A tremendous benefit of authoring a successful series is the broad-based feedback I receive from teachers and students who have used previous editions. I am sincerely grateful for their support. Virtually every change to this edition is the result of their thoughtful comments and suggestions. I hope that I have been able to take their ideas and, building upon a successful foundation of the eighth edition, make this series an even better learning and teaching tool for students and teachers. Features in the Ninth Edition Rather than provide a list of features here, that information can be found on the endpapers in the front of this book. This places the features in their proper context, as building blocks of an overall learning system that has been carefully crafted over the years to help students get the most out of the time they put into studying. Please take the time to review this and to discuss it with your students at the beginning of your course. My experience has been that when students utilize these features, they are more successful in the course. New to the Ninth Edition • Chapter Projects, which apply the concepts of each chapter to a real-world situation, have been enhanced to give students an up-to-the-minute experience. Many projects are new and Internet-based, requiring the student to research information online in order to solve problems. • Author Solves It MathXL Video Clips—author Michael Sullivan works by section through MathXL exercises typically requested by students for more explanation or tutoring. These videos are a result of Sullivan’s experiences in teaching online. • Showcase Examples are used to present examples in a guided, step-by-step format. Students can immediately see how each of the steps in a problem are employed. The “How To” examples have a two-column format in which the left column describes the step in solving the problem and the right column displays the algebra complete with annotations. • Model It examples and exercises are clearly marked with a icon.These examples and exercises are meant to develop the student’s ability to build models from both verbal descriptions and data. Many of the problems involving data require the students to first determine the appropriate model (linear, quadratic, and so on) to fit to the data and justify their choice. • Exercise Sets at the end of each section remain classified according to purpose.The “Are You Prepared?” exercises have been expanded to better serve the student who needs a just-in-time review of concepts utilized in the section. The Concepts and Vocabulary exercises have been updated. These fill-in-the-blank and True/False problems have been written to serve as reading quizzes. Mixed Practice exercises have been added where appropriate. These problems offer a comprehensive assessment of the skills learned in the section by asking problems that relate to more than one objective. Some- times these require information from previous sections so students must utilize skills learned throughout the course. Applications and Extension problems have been updated and many new problems involving sourced information and data have been added to bring relevance and timeliness to the exercises.The Explaining Concepts: Discussion and Writing exercises have been updated and reworded to stimulate discussion of concepts in online discussion forums. These can also be used to spark classroom discussion. In selected exercise sets, Interactive Exercises are presented. These applets provide a “hands-on” experience allowing students to interact with Mathematics in an active learning environment. Finally, in the Annotated Instructor’s Edition, I have preselected problems that can serve as sample homework assignments. These are indicated by a blue underline, and they are assignable in MyMathLab® if desired. • The Chapter Review now identifies Examples to review for each objective in the chapter. Changes in the Ninth Edition • CONTENT ❍ Chapter 2, Section 3 A new objective “Use a graph to locate the absolute maximum and the absolute minimum” has been added. The Extreme Value Theorem is also cited here. ❍ Chapter 3, Section 3 A new objective “Find a quadratic function given its vertex and one point” has been added. ❍ Chapter 4, Section 1 A new objective “Build cubic models from data” has been added. Preface to the Instructor
  • 16. ❍ Chapter 4, Section 5 Descartes’ Rule of Signs has been removed as its value is redundant to the information collected from other sources. ❍ Chapter 5, Section 3 The definition of an exponential function has been broadened. ❍ Chapter 9, Section 5 More applications of decom- posing vectors have been added. • ORGANIZATION ❍ Appendix A, Section A.3 The objective “Complete the Square” has been relocated to here from Section A.6. ❍ Chapter 7 The two sections on trigonometric equations, Trigonometric Equations (I) and Trigonometric Equa- tions (II), have been consolidated into a new section in Chapter 7, Section 3, entitled Trigonometric Equations. In addition, trigonometric equations that utilize specific identities have been woven into the appropriate sections throughout the remainder of Chapter 7. ❍ Chapter 9 The material on applications of vectors that was formerly in Section 5 on the Dot Product has been moved to Section 4 to emphasize the applications of the resultant vector. Using the Ninth Edition Effectively with Your Syllabus To meet the varied needs of diverse syllabi, this book contains more content than is likely to be covered in a Precalculus course. As the chart illustrates, this book has been organized with flexibility of use in mind. Within a given chapter, certain sections are optional (see the detail following the flow chart) and can be omitted without loss of continuity. Appendix A Review This chapter consists of review material. It may be used as the first part of the course or later as a just-in-time review when the content is required. Specific references to this chapter occur throughout the book to assist in the review process. Chapter 1 Graphs This chapter lays the foundation for functions. 2 1Appendix A Appendix B 10.1Ϫ10.4 10.5Ϫ10.7 9.1Ϫ9.3 3 4 5 6 12 14 1311 7 8 9.4Ϫ9.7 Chapter 2 Functions and Their Graphs Perhaps the most important chapter. Section 2.6 is optional. Chapter 3 Linear and Quadratic Functions Topic selection depends on your syllabus. Sections 3.2 and 3.4 may be omitted without a loss of continuity. Chapter 4 Polynomial and Rational Functions Topic selection depends on your syllabus. Chapter 5 Exponential and Logarithmic Functions Sections 5.1–5.6 follow in sequence. Sections 5.7, 5.8, and 5.9 are optional. Chapter 6 Trigonometric Functions Section 6.6 may be omitted in a brief course. Chapter 7 Analytic Trigonometry Section 7.7 may be omitted in a brief course. Chapter 8 Applications of Trigonometric Functions Sections 8.4 and 8.5 may be omitted in a brief course. Chapter 9 Polar Coordinates;Vectors Sections 9.1–9.3 and Sections 9.4–9.7 are independent and may be covered separately. Chapter 10 Analytic Geometry Sections 10.1–10.4 follow in sequence. Sections 10.5, 10.6, and 10.7 are independent of each other, but each requires Sections 10.1–10.4. Chapter 11 Systems of Equations and Inequalities Sections 11.2–11.7 may be covered in any order, but each requires Section 11.1. Section 11.8 requires Section 11.7. Chapter 12 Sequences; Induction;The Binomial Theorem There are three independent parts: Sections 12.1–12.3; Section 12.4; and Section 12.5. Chapter 13 Counting and Probability The sections follow in sequence. Chapter 14 A Preview of Calculus:The Limit, Derivative,and Integral of a Function If time permits, coverage of this chapter will give your students a beneficial head start in calculus. Preface to the Instructor xvii
  • 17. Acknowledgments Textbooks are written by authors, but evolve from an idea to final form through the efforts of many people. It was Don Dellen who first suggested this book and series to me. Don is remembered for his extensive contributions to publishing and mathematics. Thanks are due to the following people for their assistance and encouragement to the preparation of this edition: • From Pearson Education:Anne Kelly for her substantial contributions,ideas,and enthusiasm;Peggy Lucas,who is a huge fan and supporter; Dawn Murrin, for her unmatched talent at getting the details right; Sherry Berg of Nesbitt Graphics, Inc., for her superb organizational skills in directing production; Peggy McMahon for her leadership in overseeing production; Chris Hoag for her continued support and genuine interest; Greg Tobin for his leadership and commitment to excellence; and the Pearson Math and Science Sales team,for their continued confidence and personal support of our books. • As this book went to production,BobWalters,Production Manager, passed away after a long and valiant battle fighting lung disease. He was an old and dear friend—a true professional in every sense of the word. • Accuracy checkers: C. Brad Davis, who read the entire manuscript and accuracy checked answers. His attention to detail is amazing; Timothy Britt, for creating the Solutions Manuals and accuracy checking answers. • Reviewers: Larissa Williamson, University of Florida; Richard Nadel, Florida International University; Robin Steinberg, Puma CC; Mike Rosenthal, Florida International University; Gerardo Aladro, Florida International University; Tammy Muhs, Universty of Central Florida; Val Mohanakumar, Hillsborough CC. Finally, I offer my grateful thanks to the dedicated users and reviewers of my books, whose collective insights form the backbone of each textbook revision. My list of indebtedness just grows and grows. And, if I’ve forgotten anyone, please accept my apology. Thank you all. Roger Carlsen, Moraine Valley Community College Elena Catoiu, Joliet Junior College Mathews Chakkanakuzhi, Palomar College Tim Chappell, Penn Valley Community College John Collado, South Suburban College Alicia Collins, Mesa Community College Nelson Collins, Joliet Junior College Jim Cooper, Joliet Junior College Denise Corbett, East Carolina University Carlos C. Corona, San Antonio College Theodore C. Coskey, South Seattle Community College Donna Costello, Plano Senior High School Paul Crittenden, University of Nebraska at Lincoln John Davenport, East Texas State University Faye Dang, Joliet Junior College Antonio David, Del Mar College Stephanie Deacon, Liberty University Duane E. Deal, Ball State University Jerry DeGroot, Purdue North Central Timothy Deis, University of Wisconsin-Platteville Joanna DelMonaco, Middlesex Community College Vivian Dennis, Eastfield College Deborah Dillon, R. L.Turner High School Guesna Dohrman,Tallahassee Community College Cheryl Doolittle, Iowa State University Karen R. Dougan, University of Florida Jerrett Dumouchel, Florida Community College at Jacksonville Louise Dyson, Clark College Paul D. East, Lexington Community College Don Edmondson, University of Texas-Austin Erica Egizio, Joliet Junior College Jason Eltrevoog, Joliet Junior College Christopher Ennis, University of Minnesota Kathy Eppler, Salt Lake Community College James Africh, College of DuPage Steve Agronsky, Cal Poly State University Grant Alexander, Joliet Junior College Dave Anderson, South Suburban College Richard Andrews, Florida A&M University Joby Milo Anthony, University of Central Florida James E.Arnold, University of Wisconsin-Milwaukee Adel Arshaghi, Center for Educational Merit Carolyn Autray, University of West Georgia Agnes Azzolino, Middlesex County College Wilson P Banks, Illinois State University Sudeshna Basu, Howard University Dale R. Bedgood, East Texas State University Beth Beno, South Suburban College Carolyn Bernath,Tallahassee Community College Rebecca Berthiaume, Edison State College William H. Beyer, University of Akron Annette Blackwelder, Florida State University Richelle Blair, Lakeland Community College Kevin Bodden, Lewis and Clark College Barry Booten, Florida Atlantic University Larry Bouldin, Roane State Community College Bob Bradshaw, Ohlone College Trudy Bratten, Grossmont College Tim Bremer, Broome Community College Tim Britt, Jackson State Community College Michael Brook, University of Delaware Joanne Brunner, Joliet Junior College Warren Burch, Brevard Community College Mary Butler, Lincoln Public Schools Melanie Butler,West Virginia University Jim Butterbach, Joliet Junior College William J. Cable, University of Wisconsin-Stevens Point Lois Calamia, Brookdale Community College Jim Campbell, Lincoln Public Schools xviii Preface to the Instructor
  • 18. Preface to the Instructor xix Arthur Kaufman, College of Staten Island Thomas Kearns, North Kentucky University Jack Keating, Massasoit Community College Shelia Kellenbarger, Lincoln Public Schools Rachael Kenney, North Carolina State University Debra Kopcso, Louisiana State University Lynne Kowski, Raritan Valley Community College Yelena Kravchuk, University of Alabama at Birmingham Keith Kuchar, Manatee Community College Tor Kwembe, Chicago State University Linda J. Kyle,Tarrant Country Jr. College H.E. Lacey,Texas A & M University Harriet Lamm, Coastal Bend College James Lapp, Fort Lewis College Matt Larson, Lincoln Public Schools Christopher Lattin, Oakton Community College Julia Ledet, Lousiana State University Adele LeGere, Oakton Community College Kevin Leith, University of Houston JoAnn Lewin, Edison College Jeff Lewis, Johnson County Community College Janice C. Lyon,Tallahassee Community College Jean McArthur, Joliet Junior College Virginia McCarthy, Iowa State University Karla McCavit,Albion College Michael McClendon, University of Central Oklahoma Tom McCollow, DeVry Institute of Technology Marilyn McCollum, North Carolina State University Jill McGowan, Howard University Will McGowant, Howard University Angela McNulty, Joliet Junior College Laurence Maher, North Texas State University Jay A. Malmstrom, Oklahoma City Community College Rebecca Mann,Apollo High School Lynn Marecek, Santa Ana College Sherry Martina, Naperville North High School Alec Matheson, Lamar University Nancy Matthews, University of Oklahoma James Maxwell, Oklahoma State University-Stillwater Marsha May, Midwestern State University James McLaughlin,West Chester University Judy Meckley, Joliet Junior College David Meel, Bowling Green State University Carolyn Meitler, Concordia University Samia Metwali, Erie Community College Rich Meyers, Joliet Junior College Eldon Miller, University of Mississippi James Miller,West Virginia University Michael Miller, Iowa State University Kathleen Miranda, SUNY at Old Westbury Chris Mirbaha,The Community College of Baltimore County Val Mohanakumar, Hillsborough Community College Thomas Monaghan, Naperville North High School Miguel Montanez, Miami Dade College, Wolfson Campus Ralph Esparza, Jr., Richland College Garret J. Etgen, University of Houston Scott Fallstrom, Shoreline Community College Pete Falzone, Pensacola Junior College W.A. Ferguson, University of Illinois-Urbana/Champaign Iris B. Fetta, Clemson University Mason Flake, student at Edison Community College Timothy W. Flood, Pittsburgh State University Robert Frank,Westmoreland County Community College Merle Friel, Humboldt State University Richard A. Fritz, Moraine Valley Community College Dewey Furness, Ricke College Randy Gallaher, Lewis and Clark College Tina Garn, University of Arizona Dawit Getachew, Chicago State University Wayne Gibson, Rancho Santiago College Robert Gill, University of Minnesota Duluth Nina Girard, University of Pittsburgh at Johnstown Sudhir Kumar Goel,Valdosta State University Adrienne Goldstein, Miami Dade College, Kendall Campus Joan Goliday, Sante Fe Community College Lourdes Gonzalez, Miami Dade College, Kendall Campus Frederic Gooding, Goucher College Donald Goral, Northern Virginia Community College Sue Graupner, Lincoln Public Schools Mary Beth Grayson, Liberty University Jennifer L. Grimsley, University of Charleston Ken Gurganus, University of North Carolina James E. Hall, University of Wisconsin-Madison Judy Hall,West Virginia University Edward R. Hancock, DeVry Institute of Technology Julia Hassett, DeVry Institute-Dupage Christopher Hay-Jahans, University of South Dakota Michah Heibel, Lincoln Public Schools LaRae Helliwell, San Jose City College Celeste Hernandez, Richland College Gloria P. Hernandez, Louisiana State University at Eunice Brother Herron, Brother Rice High School Robert Hoburg,Western Connecticut State University Lynda Hollingsworth, Northwest Missouri State University Charla Holzbog, Denison High School Lee Hruby, Naperville North High School Miles Hubbard, St. Cloud State University Kim Hughes, California State College-San Bernardino Ron Jamison, Brigham Young University Richard A. Jensen, Manatee Community College Glenn Johnson, Middlesex Community College Sandra G. Johnson, St. Cloud State University Tuesday Johnson, New Mexico State University Susitha Karunaratne, Purdue University North Central Moana H. Karsteter,Tallahassee Community College Donna Katula, Joliet Junior College
  • 19. xx Preface to the Instructor Maria Montoya, Our Lady of the Lake University Susan Moosai, Florida Atlantic University Craig Morse, Naperville North High School Samad Mortabit, Metropolitan State University Pat Mower,Washburn University A. Muhundan, Manatee Community College Jane Murphy, Middlesex Community College Richard Nadel, Florida International University Gabriel Nagy, Kansas State University Bill Naegele, South Suburban College Karla Neal, Lousiana State University Lawrence E. Newman, Holyoke Community College Dwight Newsome, Pasco-Hernando Community College Denise Nunley, Maricopa Community Colleges James Nymann, University of Texas-El Paso Mark Omodt,Anoka-Ramsey Community College Seth F. Oppenheimer, Mississippi State University Leticia Oropesa, University of Miami Linda Padilla, Joliet Junior College E. James Peake, Iowa State University Kelly Pearson, Murray State University Dashamir Petrela, Florida Atlantic University Philip Pina, Florida Atlantic University Michael Prophet, University of Northern Iowa Laura Pyzdrowski,West Virginia University Neal C. Raber, University of Akron Thomas Radin, San Joaquin Delta College Aibeng Serene Radulovic, Florida Atlantic University Ken A. Rager, Metropolitan State College Kenneth D. Reeves, San Antonio College Elsi Reinhardt,Truckee Meadows Community College Jose Remesar, Miami Dade College,Wolfson Campus Jane Ringwald, Iowa State University Stephen Rodi,Austin Community College William Rogge, Lincoln Northeast High School Howard L. Rolf, Baylor University Mike Rosenthal, Florida International University Phoebe Rouse, Lousiana State University Edward Rozema, University of Tennessee at Chattanooga Dennis C. Runde, Manatee Community College Alan Saleski, Loyola University of Chicago Susan Sandmeyer, Jamestown Community College Brenda Santistevan, Salt Lake Community College Linda Schmidt, Greenville Technical College Ingrid Scott, Montgomery College A.K. Shamma, University of West Florida Martin Sherry, Lower Columbia College Carmen Shershin, Florida International University Tatrana Shubin, San Jose State University Anita Sikes, Delgado Community College Timothy Sipka,Alma College Charlotte Smedberg, University of Tampa Lori Smellegar, Manatee Community College Gayle Smith, Loyola Blakefield Leslie Soltis, Mercyhurst College John Spellman, Southwest Texas State University Karen Spike, University of North Carolina Rajalakshmi Sriram, Okaloosa-Walton Community College Katrina Staley, North Carolina Agricultural and Technical State University Becky Stamper,Western Kentucky University Judy Staver, Florida Community College-South Neil Stephens, Hinsdale South High School Sonya Stephens, Florida A&M University Patrick Stevens, Joliet Junior College John Sumner, University of Tampa Matthew TenHuisen, University of North Carolina,Wilmington Christopher Terry,Augusta State University Diane Tesar, South Suburban College Tommy Thompson, Brookhaven College Martha K.Tietze, Shawnee Mission Northwest High School Richard J.Tondra, Iowa State University Suzanne Topp, Salt Lake Community College Marilyn Toscano, University of Wisconsin, Superior Marvel Townsend, University of Florida Jim Trudnowski, Carroll College Robert Tuskey, Joliet Junior College Mihaela Vajiac, Chapman University-Orange Richard G.Vinson, University of South Alabama Jorge Viola-Prioli, Florida Atlantic University Mary Voxman, University of Idaho Jennifer Walsh, Daytona Beach Community College Donna Wandke, Naperville North High School Timothy L.Warkentin, Cloud County Community College Hayat Weiss, Middlesex Community College Kathryn Wetzel,Amarillo College Darlene Whitkenack, Northern Illinois University Suzanne Williams, Central Piedmont Community College Larissa Williamson, University of Florida Christine Wilson,West Virginia University Brad Wind, Florida International University Anna Wiodarczyk, Florida International University Mary Wolyniak, Broome Community College Canton Woods,Auburn University Tamara S.Worner,Wayne State College Terri Wright, New Hampshire Community Technical College, Manchester George Zazi, Chicago State University Steve Zuro, Joliet Junior College Michael Sullivan Chicago State University
  • 20. xxi Available to students are the following supplements: • Student Solutions Manual (ISBN 10: 0321717635; ISBN 13: 9780321717634) Fully worked solutions to odd-numbered exercises. • Algebra Review (ISBN 10: 0131480065; ISBN 13: 9780131480063) Four chapters of Intermediate Algebra Review. Perfect for a slower-paced course or for individual review. • Videos on DVD with Chapter Test Prep for Precalculus 9e (ISBN 10: 0321717546; ISBN 13: 9780321717542) The Videos on DVD contain short video clips of Michael Sullivan III working key book examples. Chapter Test Prep Videos (also included) provide fully worked solutions to the Chapter Test exercises. The Chapter Test Prep Videos are also available within MyMathLab® or on YouTube™ (go to http://www.youtube.com/SullivanPrecalc9e).Videos have optional subtitles. MathXL® Online Course (access code required) MathXL® is a powerful online homework, tutorial, and assessment system that accompanies Pearson Education’s textbooks in mathematics or statistics.With MathXL, instructors can: • Create, edit, and assign online homework and tests using algorithmically generated exercises correlated at the objective level to the textbook. • Create and assign their own online exercises and import TestGen tests for added flexibility. • Maintain records of all student work tracked in MathXL’s online gradebook. With MathXL, students can: • Take chapter tests in MathXL and receive personalized study plans based on their test results. • Use the study plan to link directly to tutorial exercises for the objectives they need to study and retest. • Access supplemental animations and video clips directly from selected exercises. MathXL is available to qualified adopters. For more information, visit our website at www.mathxl.com, or contact your Pearson sales representative. MyMathLab® Online Course (access code required) MyMathLab® is a text-specific, easily customizable online course that integrates interactive multimedia instruction with textbook content. MyMathLab gives you the tools you need to deliver all or a portion of your course online, whether your students are in a lab setting or working from home. • Interactive homework exercises, correlated to your textbook at the objective level, are algorithmically generated for unlimited practice and mastery. Most exercises are free-response and provide guided solutions, sample problems, and tutorial learning aids for extra help. • Personalized homework assignments that you can design to meet the needs of your class. MyMathLab tailors the assignment for each student based on their test or quiz scores. Each student receives a homework assignment that contains only the problems they still need to master. • Personalized Study Plan, generated when students complete a test or quiz or homework, indicates which topics have been mastered and links to tutorial exercises for topics students have not mastered. You can customize the Study Plan so that the topics available match your course content. • Multimedia learning aids, such as video lectures and podcasts, animations, and a complete multimedia textbook, help students independently improve their understanding and performance. You can assign these multimedia learning aids as homework to help your students grasp the concepts. • Homework and Test Manager lets you assign homework, quizzes, and tests that are automatically graded. Select just the right mix of questions from the MyMathLab exercise bank, instructor-created custom exercises, and/or TestGen® test items. • Gradebook, designed specifically for mathematics and statistics, automatically tracks students’ results, lets you stay on top of student performance, and gives you control over how to calculate final grades. You can also add offline (paper-and-pencil) grades to the gradebook. • MathXL Exercise Builder allows you to create static and algorithmic exercises for your online assignments. You can use the library of sample exercises as an easy starting point, or you can edit any course-related exercise. STUDENT RESOURCES
  • 21. • Pearson Tutor Center (www.pearsontutorservices.com) access is automatically included with MyMathLab. The Tutor Center is staffed by qualified math instructors who provide textbook-specific tutoring for students via toll-free phone, fax, email, and interactive Web sessions. • NEW Resources for Sullivan, Precalculus, 9e ❍ Author Solves It videos feature Mike Sullivan III working by section through MathXL exercises typically requested by students for more explanation or tutoring.These videos are a result of Sullivan’s experiences in teaching online. ❍ Sample homework assignments,preselected by the author,are indicated by a blue underline within the end-of-section exercise sets in the Annotated Instructor’s Edition and are assignable in MyMathLab. ❍ Chapter Project MathXL Exercises allow instructors to assign problems based on the new Internet-based Chapter Projects. Students do their assignments in the Flash® -based MathXL Player, which is compatible with almost any browser (Firefox® , SafariTM , or Internet Explorer® ) on almost any platform (Macintosh® or Windows® ). MyMathLab is powered by CourseCompassTM , Pearson Education’s online teaching and learning environment, and by MathXL® , our online homework, tutorial, and assessment system. MyMathLab is available to qualified adopters. For more information, visit www.mymathlab.com or contact your Pearson representative. xxii
  • 22. xxiii Acoustics amplifying sound, 344 loudness of sound, 295 loudspeaker, 548 tuning fork, 548–49 whispering galleries, 648–49, 693 Aerodynamics modeling aircraft motion, 630 Aeronautics Challenger disaster, 331 Agriculture crop allocation, 788 farm management, 783 field enclosure, 768 grazing area for cow, 539–40 minimizing cost, 783 removing stump, 602–3 Air travel bearing of aircraft, 515, 526 frequent flyer miles, 526 holding pattern, 462 parking at O’Hare International Airport, 88 revising a flight plan, 533 speed and direction of aircraft, 597–98, 601–2, 628 Archaeology age of ancient tools, 324–25 age of fossil, 330 age of tree, 330 date of prehistoric man’s death, 344 Architecture brick staircase, 808, 832 Burj Khalifa building,A15 floor design, 806–7, 832 football stadium seating, 808 mosaic design, 808, 832 Norman window, 153,A21 parabolic arch, 153 racetrack design, 651 special window, 153, 161 stadium construction, 808 window design, 153 Area of Bermuda Triangle, 539 under a curve, 447–48 of isosceles triangle, 493 of sector of circle, 360 of segment of circle, 551 Art fine decorative pieces, 378 Astronomy angle of elevation of Sun, 514 distances of planets from Sun, 802 planetary orbits, 648 Earth, 651 Jupiter, 651 Mars, 651 Mercury, 678 Neptune, 695 Pluto, 651, 695 Aviation modeling aircraft motion, 630 orbital launches, 709 speed of plane,A71 Biology alcohol and driving, 291, 296 bacterial growth, 323–24, 336–37 E-coli, 79, 119 blood types, 840–41 bone length, 161–62 cricket chirp rate and temperature, 155 healing of wounds, 281, 295 maternal age versus Down syndrome, 134 yeast biomass as function of time, 335–36 Business advertising, 133, 162 automobile production, 253–54, 726 blending coffee,A69 car rentals, 125 checkout lines, 859 cigarette exports, 337 clothing store, 861 commissions, 161 cookie orders, 788 cost of can, 210, 213 of commodity, 254 of manufacturing, 186, 219, 776–77, A13,A69 marginal, 145, 161 minimizing, 161, 783 of production, 79, 254, 752, 789 of transporting goods, 89 cost equation, 32 cost function, 126 average, 63 demand for jeans, 133 for PCs, 337 demand equation, 161, 244 depreciation, 246 discounts, 254 drive-thru rate at Burger King, 277 at Citibank, 281, 295 at McDonald’s, 281 equipment depreciation, 818 expense computation,A70 Jiffy Lube’s car arrival rate, 281, 295 managing a meat market, 783 mixing candy,A69 mixing nuts,A69 new-car markup,A81 orange juice production, 726 precision ball bearings,A13 price vs. quantity demanded, 127, 337–38 product design, 784 production scheduling, 783 product promotion, 33 profit, 752 cigar company, 102 on figurines, 790 maximizing, 781–82, 783–84 profit function, 59 rate of return on, 320 restaurant management, 710 revenue, 145, 158–59,A69 advertising and, 133 airline, 784 of clothing store, 741 daily, 145 from digital music, 102 instantaneous rate of change of, 891, 892, 901 maximizing, 145, 152 monthly, 145 theater, 711 RV rental, 163 salary, 808 gross, 58 increases in, 818, 832 sales commission on,A80 of movie theater ticket, 697, 702, 709 net, 8 profit from,A71 salvage value, 344 straight-line depreciation, 122–23, 126 supply and demand, 123–24, 126 tax, 219 toy truck manufacturing, 776–77 Applications Index
  • 23. transporting goods, 777 truck rentals, 32, 127 unemployment, 862 wages of car salesperson, 32 Calculus area under a curve, 103, 447–48 area under graph, 78 carrying a ladder around a corner, 462–63 maximizing rain gutter construction, 492–93 projectile motion, 462–63 Simpson’s rule, 153 Carpentry pitch, 33 Chemistry alpha particles, 664 decomposition reactions, 331 drug concentration, 212 pH, 294 purity of gold,A70 radioactive decay, 330, 337, 344 radioactivity from Chernobyl, 331 reactions, 153 salt solutions,A70 sugar molecules,A70–A71 volume of gas,A80 Combinatorics airport codes, 842 binary codes, 862 birthday permutations, 844, 848, 849, 855–56, 860, 862 blouses and skirts combinations, 840 book arrangements, 848, 861 box stacking, 848 code formation, 848 combination locks, 849 committee formation, 846, 848–49, 862 Senate committees, 849 flag arrangement, 847, 862 letter codes, 842, 862 letter combinations, 861 license plate possibilities, 848, 861, 863 light bulb wattage, 862 lining up people, 843, 848 number formation, 840, 848, 849, 862 objects selection, 849 seating arrangements, 861 shirts and ties combinations, 840 telephone numbers, 861 two-symbol codewords, 839 word formation, 846–47, 849, 862 Communications cell phone service, 88, 115 cell phone usage, 333–34, 339 death rates, 862 diversity index, 294–95 divorced population, 150–51 life expectancy,A80 marital status, 841 mosquito colony growth, 330 population of world, future of, 903 poverty rates, 242 rabbit colony growth, 801 Design of awning, 527 of box with minimum surface area, 212–13 of fine decorative pieces, 378 of Little League Field, 362 of water sprinkler, 361 Direction of aircraft, 597–98, 601, 628 compass heading, 602 for crossing a river, 602 of fireworks display, 663–64 of lightning strikes, 664 of motorboat, 602 of swimmer, 628 Distance Bermuda Triangle,A21 bicycle riding, 68 from Chicago to Honolulu, 448 circumference of Earth, 362 between cities, 356–57, 361 between Earth and Mercury, 527 between Earth and Venus, 527 from Earth to a star, 514–15 of explosion, 664 height of aircraft, 344, 525, 527 of bouncing ball, 818, 832 of bridge, 525 of building, 514, 515 of cloud, 510 of Eiffel Tower, 514 of embankment, 515 of Ferris Wheel rider, 462 of Great Pyramid of Cheops, 527,A21 of helicopter, 552 of hot-air balloon, 515 of Lincoln’s caricature on Mt. Rushmore, 515 of mountain, 344, 522, 525 of statue on a building, 510–11 of tower, 516 of tree, 525 of Washington Monument, 515 of Willis Tower, 515 from home, 68 from Honolulu to Melbourne, Australia, 448 cellular telephone plan, 45 installing cable TV, 108 long distance, 127 comparing phone companies, 161 phone charges, 126 satellite dish, 638–39, 640 spreading of rumors, 281, 295 Touch-Tone phones, 497, 549 Computers and computing Dell PCs, 337–38 graphics, 601 laser printers,A70 Construction of box, 768,A71 closed, 113 open, 108–9 of brick staircase, 832 of can, 242 of coffee can,A71 of cylindrical tube, 768 of enclosures around garden,A70 around pond,A70 maximizing area of, 148, 152, 161 of fencing, 148, 152, 161, 768 minimum cost for, 212 of flashlight, 640–41 of garden walk, 433 of headlight, 641 of highway, 515, 526, 552 home choices, 861 installing cable TV, 108 pitch of roof, 516 of playpen, 105–6 of rain gutter, 153, 371–72, 492–93, 506–7 of ramp, 525 access ramp, 32 of rectangular field enclosure, 152 of stadium, 153, 808 of steel drum, 213 of swimming pool,A21,A22 of swing set, 534 of tent, 538 TV dish, 640 vent pipe installation, 651 Crime income vs. rate of, 339 Cryptography matrices in, 752–53 Decorating Christmas tree,A16 Demographics age and high school diplomas, 155 birthrate of unmarried women, 145 xxiv Applications Index
  • 24. of hot-air balloon to airport, 554 from intersection, 8 from intersection, 107–8 length of guy wire, 533 of mountain trail, 515 of ski lift, 525 limiting magnitude of telescope, 344 to the Moon, 525 pendulum swings, 814, 818 to plateau, 514 across a pond, 514 range of airplane,A71 reach of ladder, 514 of rotating beacon, 415 at sea, 526, 552 to shore, 514, 526 between skyscrapers, 516, 517 surveying, 553 to tower, 527 traveled by wheel,A21 between two moving vehicles, 8 toward intersection, 107–8 between two objects, 514, 515 visibility of Gibb’s Hill Lighthouse beam, 511–12, 517,A22 visual,A22 walking, 68 width of gorge, 513 of Mississippi River, 516 of river, 509 Economics Consumer Price Index (CPI), 321 Dell personal computer price and demand, 337–38 demand equations, 244 federal stimulus package of 2009, 320 inflation, 320 IS-LM model in, 710 marginal propensity to consume, 819 multiplier, 819 participation rate, 59 per capita federal debt, 320 poverty rates, 242 poverty threshold, 9 relative income of child, 753 unemployment, 862 Education age distribution of community college, 863 college costs, 320, 818–19 college tuition and fees, 752 degrees awarded, 838 doctorate degrees awarded, 859 faculty composition, 860 field trip, 220 funding a college education, 344 grade computation,A81 high school diploma, 155 IQ tests,A81 learning curve, 282, 295 maximum level achieved, 790–91 multiple-choice test, 848 Spring break, 783 student loan, 114 interest on, 752 test design, 861 true/false test, 848 video games and grade-point average, 133 Electricity alternating current (ac), 431, 483 alternating current (ac) circuits, 406, 424 alternating current (ac) generators, 406–7 alternating voltage, 431 charging a capacitor, 549 cost of, 86–87 current in RC circuit, 282 current in RL circuit, 282, 295 impedance,A61 Kirchhoff’s Rules, 710–11, 726 light bulbs, 863 parallel circuits,A61 resistance in, 198 rates for, 32,A80 resistance, 198,A43 voltage foreign,A13 U.S.,A13 wiring, 861 Electronics loudspeakers, 548 microphones, 18 sawtooth curve, 493, 549 Energy nuclear power plant, 664 solar, 18, 609 solar heat, 641 thermostat control, 101–2 Engineering bridges clearance, 407 Golden Gate, 149–50 parabolic arch, 161, 641, 693 semielliptical arch, 651, 693 suspension, 153, 641 drive wheel, 553 Gateway Arch (St. Louis), 641 grade of road, 33 lean of Leaning Tower of Pisa, 526 moment of inertia, 497 piston engines, 378 product of inertia, 493 road system, 566 robotic arm, 619 rods and pistons, 534 searchlight, 471, 641, 693 whispering galleries, 651, 693 Entertainment cable subscribers, 338–39 Demon Roller Coaster customer rate, 281–82 movie theater, 447 theater revenues, 711 Environment lake pollution control laws, 801 oil leakage, 254 Exercise and fitness for weight loss,A80 Finance balancing a checkbook,A13 bills in wallet, 862 clothes shopping, 790 college costs, 320, 818–19 computer system purchase, 320 cost of car rental, 89 of driving car, 32 of electricity, 86–87 of fast food, 710 of land, 553 minimizing, 161, 212 of natural gas, 88 of trans-Atlantic travel, 59, 67 of triangular lot, 538 cost function, 126 cost minimization, 145 credit cards debt, 801 interest on, 319 payment, 89, 801 depreciation, 281, 339 of car, 311, 347–48 discounts, 254 division of money,A64,A69 electricity rates, 32 federal income tax,A80 federal stimulus package of 2009, 320 financial planning, 709–10, 722–23, 725, A64,A69 foreign exchange, 254 funding a college education, 344 future value of money, 186–87 gross salary, 58 income vs. crime rate, 339 life cycle hypothesis, 154 Applications Index xxv
  • 25. xxvi Applications Index loans,A69 car, 801 interest on, 114, 752,A64 repayment of, 319 student, 752 mortgages interest rates on, 320 second, 320 phone charges, long distance, 127 price appreciation of homes, 319 prices of fast food, 711 price vs. quantity demanded, 127 refunds, 710 revenue maximization, 145, 146–47, 152 rich man’s promise, 819 salary options, 819–20 saving for a car, 319 for a home, 818 savings accounts interest, 320 sinking fund, 818–19 taxes, 126 e-filing returns, 79 federal income, 89, 266 luxury, 126 used-car purchase, 319 water bills,A80–A81 Food and nutrition animal, 784 candy, 132 color mix of candy, 863 cooler contents, 863 cooling time of pizza, 330 fast food, 710, 711 Girl Scout cookies, 859 hospital diet, 711, 725 ice cream, 783 “light” foods,A81 number of possible meals, 838–39 pig roasts, 331 raisins, 132–33 warming time of Beer stein, 331 Forestry wood product classification, 329 Games die rolling, 863 grains of wheat on a chess board, 819 Powerball, 863 Gardens and gardening.See also Landscaping enclosure for,A70 Geography area of Bermuda Triangle, 539 area of lake, 539, 553 inclination of hill, 597 inclination of mountain trail, 509, 552 Geology earthquakes, 296 Geometry angle between two lines, 483 balloon volume, 253 circle area of, 539,A69 center of, 40 circumference of,A12,A69 inscribed in square, 107 length of chord of, 534 radius of, 40, 768 collinear points, 736 cone volume, 254 cube length of edge of, 233 surface area of,A13 volume of,A13 cylinder inscribing in cone, 108 inscribing in sphere, 108 volume of, 254 Descartes’s method of equal roots, 768 equation of line, 736 ladder angle, 554 quadrilateral area, 555 rectangle area of, 58, 104–5,A12 dimensions of, 768 inscribed in semicircle, 107, 493 perimeter of,A12 semicircle inscribed in, 107 semicircle area, 538, 555 sphere surface area of,A13 volume of,A13 square area of,A21,A69 perimeter of,A69 surface area of balloon, 253 of cube,A13 of sphere,A13 triangle area of, 538, 539, 555, 736,A13 circumscribing, 528 equilateral,A13 inscribed in circle, 107 isosceles, 58, 555, 768 Pascal’s, 801 perimeter of,A13 right, 513 sides of, 555 volume of parallelepiped, 625 Government federal deficit, 344 federal income tax, 59, 89, 266,A80 e-filing returns, 79 federal stimulus package of 2009, 320 first-class mail, 89 per capita federal debt, 320 Health.See also Medicine age vs. total cholesterol, 339 blood pressure, 462 cigarette use among teens, 32–33 expenditures on, 59 heartbeats during exercise, 120–21 ideal body weight, 266 life cycle hypothesis, 154 Home improvement.See also Construction painting a house, 711 Housing apartment rental, 154 number of rooms in, 58 price appreciation of homes, 319 Investment(s) annuity, 815–16, 818 in bonds, 784 Treasuries, 725, 726, 774, 776, 778 zero-coupon, 317, 320–21 in CDs, 784 compound interest on, 312–13, 314, 315–16, 319–20 diversified, 711 division among instruments,A69 doubling of, 317–18, 321 finance charges, 319 in fixed-income securities, 320–21, 784 401K, 818, 832 growth rate for, 319–20 IRA, 320, 344, 815–16, 818, 832 money market account, 316 return on, 319–20, 783, 784 savings account, 315–16 in stock analyzing, 164 appreciation, 319–20 NASDAQ stocks, 848 NYSE stocks, 848 portfolios of, 841 price of, 819 time to reach goal, 319, 321 tripling of, 318, 321 Landscaping.See also Gardens and gardening building a walk, 433 height of tree, 525
  • 26. Applications Index xxvii pond enclosure, 161 rectangular pond border, 161 removing stump, 602–3 tree planting, 725 watering lawn, 361 Law and law enforcement motor vehicle thefts, 859 violent crimes, 59 Leisure and recreation cable TV, 108 community skating rink, 114 Ferris wheel, 39, 462, 527, 548 field trip, 220 video games and grade-point average, 133 Marketing Dell personal computer price and demand, 337–38 Measurement optical methods of, 471 of rainfall, 609 Mechanics.See Physics Medicine.See also Health age vs. total cholesterol, 339 blood pressure, 462 drug concentration, 79, 212 drug medication, 281, 295 healing of wounds, 281, 295 spreading of disease, 345 Meteorology weather balloon height and atmospheric pressure, 334–35 Miscellaneous banquet seating, 783 bending wire, 768 biorhythms, 407 carrying a ladder around a corner, 415, 462–63 citrus ladders, 808 coffee container, 348 cross-sectional area of beam, 59, 66 curve fitting, 710, 725, 788 drafting error, 8 Mandelbrot sets, 589 pet ownership, 859 rescue at sea, 522–23, 525 surface area of balloon, 253 surveillance satellites, 516–17 volume of balloon, 253 wire enclosure area, 107 working together on a job,A70 Mixtures.See also Chemistry blending coffees, 777, 788, A64–A65,A69 blending teas,A69 cement,A71 mixed nuts, 709, 777, 788,A69 mixing candy,A69 water and antifreeze,A70 Motion,549.See also Physics catching a train, 694 on a circle, 361 of Ferris Wheel rider, 462 of golf ball, 66 minute hand of clock, 360, 431 objects approaching intersection, 690 of pendulum, 549 revolutions of circular disk,A21 simulating, 684 tortoise and the hare race, 768 uniform, 690,A65–A67,A69–A70 Motor vehicles alcohol and driving, 291, 296 approaching intersection, 690 automobile production, 253–54, 726 average car speed,A71 brake repair with tune-up, 862 braking load, 609–10, 628 crankshafts, 526 depreciation of, 246, 311, 339, 347–48 gas mileage and speed and, 154–55 with Global Positioning System (GPS), 345 loans for, 801 new-car markup,A81 runaway car, 159 spin balancing tires, 362, 431 stopping distance, 145, 266 used-car purchase, 319 Music revenues from, 102 Navigation avoiding a tropical storm, 533 bearing, 511–12, 532 of aircraft, 515, 526 of ship, 515, 553 commercial, 525–26 compass heading, 602 crossing a river, 602 error in correcting, 530–31, 552 time lost due to, 526 rescue at sea, 522–23, 525 revising a flight plan, 533 Oceanography tides, 425–26 Optics angle of refraction, 463–64 bending light, 464 index of refraction, 463–64 laser beam, 514 laser projection, 493 lensmaker’s equation,A43 light obliterated through glass, 281 mirrors, 664 reflecting telescope, 641 Pediatrics height vs. head circumference, 133, 266 Pharmacy vitamin intake, 710, 726 Photography camera distance, 515 Physics angle of elevation of Sun, 514 bouncing balls, 832 braking load, 610 damped motion, 544 Doppler effect, 212 effect of elevation on weight, 67 force, 601,A69 to hold a wagon on a hill, 607 resultant, 601 gravity, 198, 220 on Earth, 58, 266 on Jupiter, 58 harmonic motion, 543 heat transfer, 462 inclination of mountain trail, 509 kinetic energy,A69 missile trajectory, 164 moment of inertia, 497 motion of object, 543 pendulum motion, 360, 549, 814,A90 period, 102, 267 pressure,A69 product of inertia, 493 projectile motion, 148–49, 152, 377–79, 462, 463, 487–88, 493, 497, 682–83, 689–91, 694 artillery, 159, 453 thrown object, 689 simulating motion, 684 static equilibrium, 598–99, 602, 603, 628 tension, 598–99, 602, 628 thrown object ball, 154, 158, 889–90, 891 truck pulls, 602 uniform motion, 107–8, 690, 694, A65–A67,A69–A70 velocity down inclined planes,A89
  • 27. xxviii Applications Index vertically propelled object, 158 weight of a boat, 602 of a car, 602 of a piano, 598 work, 619,A69 Play swinging, 555 wagon pulling, 601, 608 Population.See also Demographics bacterial, 330, 331, 336–37 decline in, 330 E-coli growth, 79, 119 of endangered species, 331 of fruit fly, 328 as function of age, 58 growth in, 330, 331 insect, 198, 330 of trout, 801 of United States, 311, 338, 834 of world, 311, 338, 344, 792 Probability checkout lines, 859 classroom composition, 859 “Deal or No Deal”TV show, 835 exponential, 277, 281, 295 household annual income, 859 Monty Hall Game, 863–64 Poisson, 281–82 “Price is Right” games, 859 of winning a lottery, 860 Publishing page design, 113 Pyrotechnics fireworks display, 663–64 Rate.See also Speed of car, 361 catching a bus, 689 catching a train, 689 current of stream, 710 of emptying oil tankers,A71 a pool,A71 a tub,A71 to keep up with the Sun, 362 revolutions per minute of bicycle wheels, 361 of pulleys, 363 speed average,A71 of current,A69–A70 of motorboat,A69–A70 of moving walkways,A70 per gallon rate and, 154–55 of plane,A71 golf, 66, 682–83, 690 distance to the green, 532 sand bunkers, 453 hammer throw, 433 Olympic heroes,A71 Olympic performance, 43–44 races, 765–66, 768,A71 relay runners, 861 swimming, 554, 628 tennis,A70 Statistics.See Probability Surveying distance between houses, 553 Surveys of appliance purchases, 840 data analysis, 837–38, 840 stock portfolios, 841 of summer session attendance, 840 of TV sets in a house, 859 Temperature of air parcel, 808 body,A13 conversion of, 254, 266 cooling time of pizza, 330 cricket chirp rate and, 155 measuring, 32 after midnight, 186 monthly, 424–25, 432 of portable heater, 345 relationship between scales, 102 sinusoidal function from, 420–21 of skillet, 344 warming time of Beer stein, 331 wind chill factor, 345 Tests and testing IQ,A81 Time for Beer stein to warm, 331 for block to slide down inclined plane, 378 Ferris Wheel rider height as function of, 462 to go from an island to a town, 108 hours of daylight, 244, 349, 422–23, 426, 432, 434, 447 for pizza to cool, 330 of sunrise, 362, 447 of trip, 378, 392 Transportation deicing salt, 453 Niagara Falls Incline Railway, 515 Real estate commission schedule,A80 cost of land, 553 cost of triangular lot, 538 Recreation bungee jumping, 219 Demon Roller Coaster customer rate, 281–82 online gambling, 859 Security security cameras, 514 Seismology calibrating instruments, 694 Sequences.See also Combinatorics ceramic tile floor design, 806–7 Drury Lane Theater, 808 football stadium seating, 808 seats in amphitheater, 808 Speed of aircraft, 601, 628 angular, 361, 431 of current, 361–62, 788 as function of time, 68, 107–8 instantaneous of ball, 891, 901 on the Moon, 892 of parachutist, 901 of jet stream, 788 linear, 358–59 on Earth, 361 of merry-go-rounds, 431 of Moon, 361 revolutions per minute of pulley, 361 of rotation of lighthouse beacons, 431 of swimmer, 628 of truck, 514 of wheel pulling cable cars, 362 wind, 710 Sports baseball, 690, 849, 861 diamond, 8 dimensions of home plate, 538 field, 533, 534 Little League, 8, 362–63 on-base percentage, 128–29 stadium, 533 World Series, 849 basketball, 849 free throws, 66, 516 granny shots, 66 biathlon,A71 bungee jumping, 219 exacta betting, 863 football, 651,A70
  • 28. Applications Index xxix Travel.See also Air travel; Navigation bearing, 526, 553 drivers stopped by the police, 347 parking at O’Hare International Airport, 88 Volume of gasoline in tank,A89 of ice in skating rink, 114 of water in cone, 108 rainfall measurement, 609 relative humidity, 282 weather satellites, 39 wind chill, 89, 345 Work,608 computing, 608, 609, 628 constant rate jobs, 788 pulling a wagon, 608 ramp angle, 610 wheel barrow push, 601 Weapons artillery, 159, 453 cannons, 164 Weather atmospheric pressure, 281, 295 avoiding a tropical storm, 533 cooling air, 808 hurricanes, 186 lightning strikes, 660–61, 664
  • 29. Photo Credits xxx Chapter 1 Pages 1 and 43, Getty Images; Page 18, DOE Digital Photo Archive; Page 32 Tetra Images/Alamy; Page 39, Jasonleehl/Shutterstock. Chapter 2 Pages 45 and 115, Stephen Coburn/Shutterstock; Page 58, JPL-Caltech/NASA; Page 66, Exactostock/SuperStock; Page 102, Kg Kua/Dreamstime. Chapter 3 Pages 117 and 164, Peter Morgan/AP Images; Page 153, Sajko/Shutterstock. Chapter 4 Pages 165 and 244, Ivanova Inga/Shutterstock; Page 213, Oonai/Stockphoto. Chapter 5 Pages 246 and 347,Thinkstock; Page 302, Getty Images; Page 311 col. 1, Stockbyte/Thinkstock; Page 311 col. 2,Transtock/SuperStock; Page 316, iStockphoto/Thinkstock; Page 331, JuniperImages/Thinkstock. Chapter 6 Pages 349 and 434, Nova for Widows, http://www.nisa.com; Page 361, Ryan McVay/Thinkstock; Page 407, Srdjan Draskovic/Dreamstime. Chapter 7 Pages 435 and 503, Exaxion/iStockphoto Image. Chapter 8 Pages 504 and 556, PhotoDisc/Getty Images; Page 516, Sergey Karpov/Shutterstock; Page 539,Alexandre Fagundes De Fagundes/Dreamstime; Page 541, iStockphoto/ Thinkstock. Chapter 9 Pages 557 and 630, Igmax/iStockphoto; Page 579, North Wind Picture Archive/Alamy; Page 587, SSPL/Getty Images; Page 599, Hulton Archive/Getty Images. Chapter 10 Pages 631 and 695, JPL/Caltech/NASA; Page 649,Thomas Barrat/Shutterstock. Chapter 11 Pages 696 and 790, Rob Crandall/Stock Connection/Alamy; Page 750, SSPL/Getty Images. Chapter 12 Pages 792 and 834,Albo/Shutterstock Image. Chapter 13 Pages 835 and 863,Trae Patton/NBCU Photo Bank/AP Images; Page 856, Thinkstock. Chapter 14 Pages 865 and 903, Rafael Macia/Photo Researchers, Inc. Appendix A Page A15, Hainaultphoto/Shutterstock; Page A21, Problem 51,Whole Spirit Press; Page A21, Problem 52, Red River Press, Inc.
  • 30. PRECALCULUS N I N T H E D I T I O N
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  • 32. 1 In Appendix A, we review algebra essentials, geometry essentials, and equations in one variable. Here we connect algebra and geometry using the rectangular coordinate system to graph equations in two variables. The idea of using a system of rectangular coordinates dates back to ancient times, when such a system was used for surveying and city planning. Apollonius of Perga, in 200 BC, used a form of rectangular coordinates in his work on conics, although this use does not stand out as clearly as it does in modern treatments. Sporadic use of rectangular coordinates continued until the 1600s. By that time, algebra had developed sufficiently so that René Descartes (1596–1650) and Pierre de Fermat (1601–1665) could take the crucial step, which was the use of rectangular coordinates to translate geometry problems into algebra problems, and vice versa. This step was important for two reasons. First, it allowed both geometers and algebraists to gain new insights into their subjects, which previously had been regarded as separate, but now were seen to be connected in many important ways. Second, these insights made the development of calculus possible, which greatly enlarged the number of areas in which mathematics could be applied and made possible a much deeper understanding of these areas. Graphs Outline The First Modern Olympics: Athens, 1896 The birth of the modern Olympic Games By John Gettings—“I hereby proclaim the opening of the first International Olympic Games at Athens.”With these words on April 6, 1896, King George I of Greece welcomed the crowd that had gathered in the newly reconstructed Panathenean Stadium to the modern-day Olympic Summer Games. The event was the idea of Baron Pierre de Coubertin of France who traveled the world to gather support for his dream to have nations come together and overcome national disputes, all in the name of sport. The program for the Games included track and field, fencing, weightlifting, rifle and pistol shooting, tennis, cycling, swimming, gymnastics, and wrestling. Although 14 nations participated, most of the athletes were Greek. The Games reached their high point on Day 5 with the first modern-day marathon. The idea to hold an event to commemorate the Ancient Olympic games was suggested by a friend of de Coubertin and was met with great anticipation.The race was run from Marathon to Athens (estimated at 22–26 miles), watched by more than 100,000 people, and won by a Greek runner, Spiridon Louis. Gettings,The First Modern Olympics: Athens, 1986, © 2000–2010 Pearson Education, publishing as Infoplease. Reprinted with permission. —See the Internet-based Chapter Project— 1.1 The Distance and Midpoint Formulas 1.2 Graphs of Equations inTwoVariables;Intercepts;Symmetry 1.3 Lines 1.4 Circles • Chapter Review • ChapterTest • Chapter Project
  • 33. 2 CHAPTER 1 Graphs x y –4 –2 42 2 –2 4 –4 O Figure 1 Rectangular Coordinates We locate a point on the real number line by assigning it a single real number, called the coordinate of the point. For work in a two-dimensional plane, we locate points by using two numbers. We begin with two real number lines located in the same plane: one horizontal and the other vertical. The horizontal line is called the x-axis, the vertical line the y-axis, and the point of intersection the origin O. See Figure 1.We assign coordinates to every point on these number lines using a convenient scale. We usually use the same scale on each axis, but in applications, different scales appropriate to the application may be used. The origin O has a value of 0 on both the x-axis and y-axis. Points on the x-axis to the right of O are associated with positive real numbers, and those to the left of O are associated with negative real numbers. Points on the y-axis above O are associated with positive real numbers, and those below O are associated with negative real numbers. In Figure 1, the x-axis and y-axis are labeled as x and y, respectively, and we have used an arrow at the end of each axis to denote the positive direction. The coordinate system described here is called a rectangular or Cartesian* coordinate system. The plane formed by the x-axis and y-axis is sometimes called the xy-plane, and the x-axis and y-axis are referred to as the coordinate axes. Any point P in the xy-plane can be located by using an ordered pair of real numbers. Let x denote the signed distance of P from the y-axis (signed means that, if P is to the right of the y-axis, then and if P is to the left of the y-axis, then ); and let y denote the signed distance of P from the x-axis. The ordered pair also called the coordinates of P, then gives us enough information to locate the point P in the plane. For example, to locate the point whose coordinates are go 3 units along the x-axis to the left of O and then go straight up 1 unit.We plot this point by placing a dot at this location. See Figure 2, in which the points with coordinates , and are plotted. The origin has coordinates .Any point on the x-axis has coordinates of the form and any point on the y-axis has coordinates of the form If are the coordinates of a point P, then x is called the x-coordinate, or abscissa, of P and y is the y-coordinate, or ordinate, of P.We identify the point P by its coordinates by writing . Usually, we will simply say “the point ” rather than “the point whose coordinates are .” The coordinate axes divide the xy-plane into four sections called quadrants, as shown in Figure 3. In quadrant I, both the x-coordinate and the y-coordinate of all points are positive; in quadrant II, x is negative and y is positive; in quadrant III, both x and y are negative; and in quadrant IV, x is positive and y is negative. Points on the coordinate axes belong to no quadrant. Now Work P R O B L E M 1 3 1x, y21x, y2 P = 1x, y21x, y2 1x, y2 10, y2.1x, 02, 10, 02 13, 221-2, -32, 13, -22 1-3, 12, 1-3, 12, 1x, y2, x 6 0 x 7 0, 1x, y2 *Named after René Descartes (1596–1650), a French mathematician, philosopher, and theologian. x y –4 4 1 3 2 2 3 3 2 4 (3, 2) 3 (–3, 1) (–2, –3) (3, –2) O Figure 2 x y Quadrant I x > 0, y > 0 Quadrant IV x > 0, y < 0 Quadrant II x < 0, y > 0 Quadrant III x < 0, y < 0 Figure 3 1.1 The Distance and Midpoint Formulas • Algebra Essentials (Appendix A, Section A.1, pp.A1–A10) • Geometry Essentials (Appendix A, Section A.2, pp.A14–A19) PREPARING FOR THIS SECTION Before getting started, review the following: Now Work the ‘Are You Prepared?’ problems on page 6. OBJECTIVES 1 Use the Distance Formula (p.3) 2 Use the Midpoint Formula (p.5)
  • 34. SECTION 1.1 The Distance and Midpoint Formulas 3 COMMENT On a graphing calculator, you can set the scale on each axis. Once this has been done, you obtain the viewing rectangle. See Figure 4 for a typical viewing rectangle. You should now read Section B.1, The Viewing Rectangle, in Appendix B. ᭿ Figure 4 1 Use the Distance Formula If the same units of measurement, such as inches, centimeters, and so on, are used for both the x-axis and y-axis, then all distances in the xy-plane can be measured using this unit of measurement. Finding the Distance between Two Points Find the distance d between the points and .15, 6211, 32 EXAMPLE 1 Solution First plot the points and and connect them with a straight line. See Figure 5(a). We are looking for the length d. We begin by drawing a horizontal line from to and a vertical line from to forming a right triangle, as shown in Figure 5(b). One leg of the triangle is of length 4 (since ), and the other is of length 3 (since ). By the Pythagorean Theorem, the square of the distance d that we seek is d = 225 = 5 d2 = 42 + 32 = 16 + 9 = 25 ƒ6 - 3ƒ = 3 ƒ5 - 1ƒ = 4 15, 62,15, 3215, 3211, 32 15, 6211, 32 THEOREM Distance Formula The distance between two points and denoted by is (1)d1P1, P22 = 41x2 - x122 + 1y2 - y122 d1P1, P22, P2 = 1x2, y22,P1 = 1x1, y12 Proof of the Distance Formula Let denote the coordinates of point and let denote the coordinates of point . Assume that the line joining and is neither horizontal nor vertical. Refer to Figure 6(a) on page 4. The coordinates of are .The horizontal distance from to is the absoluteP3P11x2, y12P3 P2P1 P21x2, y22 P11x1, y12 x y 3 (1, 3) (5, 6) 3 4 d 6 (b) 6 3 (5, 3) x y 3 (1, 3) (5, 6) d 6 (a) 6 3 Figure 5 In Words To compute the distance between two points, find the difference of the x-coordinates, square it, and add this to the square of the difference of the y-coordinates. The square root of this sum is the distance. The distance formula provides a straightforward method for computing the distance between two points. ᭹
  • 35. 4 CHAPTER 1 Graphs value of the difference of the x-coordinates, . The vertical distance from to is the absolute value of the difference of the y-coordinates, . See Figure 6(b). The distance that we seek is the length of the hypotenuse of the right triangle, so, by the Pythagorean Theorem, it follows that d1P1, P22 = 41x2 - x122 + 1y2 - y122 = 1x2 - x122 + 1y2 - y122 3d1P1, P2242 = ƒx2 - x1ƒ2 + ƒy2 - y1ƒ2 d1P1, P22 ƒy2 - y1ƒP2P3 ƒx2 - x1ƒ P1 ϭ (x1, y1) x1 (a) x2 P3 ϭ (x2, y1) y y x x P2 ϭ (x2 , y2 )y2 y1 (b) x1 x2 P2 ϭ (x2, y2) y2 y1 P1 ϭ (x1 , y1 ) d(P1 , P2 ) P3 ϭ (x2, y1)⏐x2 Ϫ x1⏐ ⏐y2 Ϫ y1⏐ Figure 6 Now, if the line joining and is horizontal, then the y-coordinate of equals the y-coordinate of that is, Refer to Figure 7(a). In this case, the distance formula (1) still works, because, for it reduces to d1P1, P22 = 41x2 - x122 + 02 = 41x2 - x122 = ƒx2 - x1ƒ y1 = y2, y1 = y2.P2; P1P2P1 ⏐x2 Ϫ x1⏐ x1 x2 y1 x y P2 ϭ (x2, y1)P1 ϭ (x1, y1) d(P1, P2) (a) ⏐y2 Ϫ y1⏐ x1 y1 y2 P2 ϭ (x1 , y2 ) P1 ϭ (x1, y1) d(P1, P2) x y (b) Figure 7 A similar argument holds if the line joining and is vertical. See Figure 7(b). ᭿ P2P1 Using the Distance Formula Find the distance d between the points and (3, 2).1-4, 52 EXAMPLE 2 Solution Using the distance formula, equation (1), the distance d is Now Work P R O B L E M S 1 7 A N D 2 1 The distance between two points and is never a negative number. Furthermore, the distance between two points is 0 only when the points are identical, that is, when and . Also, because and , it makes no difference whether the distance is computed from or from ; that is, . The introduction to this chapter mentioned that rectangular coordinates enable us to translate geometry problems into algebra problems, and vice versa. The next example shows how algebra (the distance formula) can be used to solve geometry problems. d1P2, P12d1P1, P22 =P2 to P1P1 to P2 1y1 - y222 1y2 - y122 =1x1 - x222 1x2 - x122 =y1 = y2x1 = x2 P2 = 1x2, y22P1 = 1x1, y12 = 249 + 9 = 258 L 7.62 d = 233 - 1-4242 + 12 - 522 = 272 + 1-322 ᭹
  • 36. SECTION 1.1 The Distance and Midpoint Formulas 5 Using Algebra to Solve Geometry Problems Consider the three points and . (a) Plot each point and form the triangle ABC. (b) Find the length of each side of the triangle. (c) Verify that the triangle is a right triangle. (d) Find the area of the triangle. C = 13, 12A = 1-2, 12, B = 12, 32, EXAMPLE 3 Solution (a) Figure 8 shows the points A, B, C and the triangle ABC. (b) To find the length of each side of the triangle, use the distance formula, equation (1). (c) To show that the triangle is a right triangle, we need to show that the sum of the squares of the lengths of two of the sides equals the square of the length of the third side. (Why is this sufficient?) Looking at Figure 8, it seems reasonable to conjecture that the right angle is at vertex B. We shall check to see whether Using the results in part (b), It follows from the converse of the Pythagorean Theorem that triangle ABC is a right triangle. (d) Because the right angle is at vertex B, the sides AB and BC form the base and height of the triangle. Its area is Now Work P R O B L E M 2 9 Area = 1 2 1Base21Height2 = 1 2 A225B A 25B = 5 square units = 20 + 5 = 25 = 3d1A, C242 3d1A, B242 + 3d1B, C242 = A225B2 + A 25B2 3d1A, B242 + 3d1B, C242 = 3d1A, C242 d1A, C2 = 433 - 1-2242 + 11 - 122 = 225 + 0 = 5 d1B, C2 = 413 - 222 + 11 - 322 = 21 + 4 = 25 d1A, B2 = 432 - 1-2242 + 13 - 122 = 216 + 4 = 220 = 225 2 Use the Midpoint Formula We now derive a formula for the coordinates of the midpoint of a line segment. Let and be the endpoints of a line segment, and let be the point on the line segment that is the same distance from as it is from See Figure 9. The triangles and are congruent. Do you see why? is given; * and . So, we have angle–side–angle. Because triangles and are congruent, corresponding sides are equal in length.That is, x = x1 + x2 2 y = y1 + y2 2 2x = x1 + x2 2y = y1 + y2 x - x1 = x2 - x and y - y1 = y2 - y MBP2P1AM∠MP2B ∠P1MA =∠AP1M = ∠BMP2d1P1, M2 = d1M, P22 MBP2P1AMP2. P1M = 1x, y2 P2 = 1x2, y22P1 = 1x1, y12 *A postulate from geometry states that the transversal forms congruent corresponding angles with the parallel line segments and .MBP1A P1P2 x y –3 3 3 C = (3, 1) B = (2, 3) A = (–2, 1) Figure 8 x1 x2x y1 x y A = (x, y1 ) M = (x, y) P1 = (x1 , y1 ) x – x1 x2 – x y2 – y y – y1 P2 = (x2, y2) B = (x2 , y) y y2 Figure 9 ᭹
  • 37. 6 CHAPTER 1 Graphs THEOREM Midpoint Formula Themidpoint ofthelinesegmentfrom to is (2)M = 1x, y2 = ¢ x1 + x2 2 , y1 + y2 2 ≤ P2 = 1x2, y22P1 = 1x1, y12M = 1x, y2 Finding the Midpoint of a Line Segment Find the midpoint of the line segment from to . Plot the points and and their midpoint.P2P1 P2 = 13, 12P1 = 1-5, 52 EXAMPLE 4 Solution Apply the midpoint formula (2) using and . Then the coordinates of the midpoint M are That is, . See Figure 10. Now Work P R O B L E M 3 5 M = 1-1, 32 x = x1 + x2 2 = -5 + 3 2 = -1 and y = y1 + y2 2 = 5 + 1 2 = 3 1x, y2 y2 = 1x1 = -5, y1 = 5, x2 = 3, x y 5 5–5 P2 ϭ (3, 1) P1 ϭ (–5, 5) M ϭ (–1, 3) Figure 10 ᭹ 7. If are the coordinates of a point P in the xy-plane, then x is called the of P and y is the of P. 8. The coordinate axes divide the xy-plane into four sections called . 9. If three distinct points P, Q, and R all lie on a line and if then Q is called the of the line segment from P to R. d1P, Q2 = d1Q, R2, 1x, y2 10. True or False The distance between two points is some- times a negative number. 11. True or False The point lies in quadrant IV of the Cartesian plane. 12. True or False The midpoint of a line segment is found by averaging the x-coordinates and averaging the y-coordinates of the endpoints. 1-1, 42 Concepts and Vocabulary ‘Are You Prepared?’ Answers are given at the end of these exercises. If you get a wrong answer, read the pages listed in red. 1. On the real number line the origin is assigned the number . (p.A4) 2. If and 5 are the coordinates of two points on the real number line, the distance between these points is . (pp.A5–A6) 3. If 3 and 4 are the legs of a right triangle, the hypotenuse is . (p.A14) 4. Use the converse of the Pythagorean Theorem to show that a triangle whose sides are of lengths 11, 60, and 61 is a right triangle. (pp.A14–A15) -3 5. The area A of a triangle whose base is b and whose altitude is h is A ϭ . (p.A15) 6. True or False Two triangles are congruent if two angles and the included side of one equals two angles and the included side of the other. (pp.A16–A17) 1.1 Assess Your Understanding In Problems 13 and 14, plot each point in the xy-plane.Tell in which quadrant or on what coordinate axis each point lies. 13. (a) (b) (c) C = 1-2, -22 B = 16, 02 A = 1-3, 22 14. (a) (b) (c) C = 1-3, 42 B = 1-3, -42 A = 11, 42 Skill Building (d) (e) (f) F = 16, -32 E = 10, -32 D = 16, 52 (d) (e) (f) F = 1-3, 02 E = 10, 12 D = 14, 12 In Words To find the midpoint of a line segment, average the x-coordinates and average the y-coordinates of the endpoints.
  • 38. SECTION 1.1 The Distance and Midpoint Formulas 7 15. Plot the points and . Describe the set of all points of the form where y is a real number. 16. Plot the points , and . Describe the set of all points of the form where x is a real number. In Problems 17–28, find the distance between the points and P2.P1d1P1, P22 1x, 32,1-4, 3215, 321-2, 32,11, 32,10, 32, 12, y2,12, -1212, 12,12, 42,12, -32,12, 02, 17. 18. 19. 20. P1 = (0, 0) P2 = (2, 1) x y –2 –1 2 2 P1 = (0, 0)P2 = (–2, 1) x y –2 –1 2 2 –1 x y 2 2–2 P2 ϭ (–2, 2) P1 ϭ (1, 1) x y –2 –1 2 2P1 = (–1, 1) P2 = (2, 2) 21. P1 = 13, -42; P2 = 15, 42 22. P1 = 1-1, 02; P2 = 12, 42 23. P1 = 1-3, 22; P2 = 16, 02 24. P1 = 12, -32; P2 = 14, 22 25. P1 = 14, -32; P2 = 16, 42 26. P1 = 1-4, -32; P2 = 16, 22 27. P1 = 1a, b2; P2 = 10, 02 28. P1 = 1a, a2; P2 = 10, 02 29. A = 1-2, 52; B = 11, 32; C = 1-1, 02 30. A = 1-2, 52; B = 112, 32; C = 110, -112 31. A = 1-5, 32; B = 16, 02; C = 15, 52 32. A = 1-6, 32; B = 13, -52; C = 1-1, 52 33. A = 14, -32; B = 10, -32; C = 14, 22 34. A = 14, -32; B = 14, 12; C = 12, 12 35. P1 = 13, -42; P2 = 15, 42 36. P1 = 1-2, 02; P2 = 12, 42 37. P1 = 1-3, 22; P2 = 16, 02 38. P1 = 12, -32; P2 = 14, 22 39. P1 = 14, -32; P2 = 16, 12 40. P1 = 1-4, -32; P2 = 12, 22 41. P1 = 1a, b2; P2 = 10, 02 42. P1 = 1a, a2; P2 = 10, 02 In Problems 29–34, plot each point and form the triangle ABC.Verify that the triangle is a right triangle. Find its area. In Problems 35–42, find the midpoint of the line segment joining the points and P2.P1 43. If the point is shifted 3 units to the right and 2 units down, what are its new coordinates? 44. If the point is shifted 2 units to the left and 4 units up, what are its new coordinates? 45. Find all points having an x-coordinate of 3 whose distance from the point is 13. (a) By using the Pythagorean Theorem. (b) By using the distance formula. 46. Find all points having a y-coordinate of whose distance from the point is 17. (a) By using the Pythagorean Theorem. (b) By using the distance formula. 47. Find all points on the x-axis that are 6 units from the point . 48. Find all points on the y-axis that are 6 units from the point . 49. The midpoint of the line segment from P1 to P2 is . If , what is ? 50. The midpoint of the line segment from to is . If what is ? 51. Geometry The medians of a triangle are the line segments from each vertex to the midpoint of the opposite side (see the figure). Find the lengths of the medians of the triangle with vertices at , and .C = 14, 42A = 10, 02, B = 16, 02 P1P2 = 17, -22, 15, -42P2P1 P2P1 = 1-3, 62 1-1, 42 14, -32 14, -32 11, 22 -6 1-2, -12 1-1, 62 12, 52 52. Geometry An equilateral triangle is one in which all three sides are of equal length. If two vertices of an equilateral triangle are and find the third vertex. How many of these triangles are possible? 10, 02,10, 42 Applications and Extensions Median A B C Midpoint 53. Geometry Find the midpoint of each diagonal of a square with side of length s. Draw the conclusion that the diagonals of a square intersect at their midpoints. [Hint: Use (0, 0), (0, s), (s, 0), and (s, s) as the vertices of the square.] 54. Geometry Verify that the points (0, 0), (a, 0), and are the vertices of an equilateral triangle. Then show that the midpoints of the three sides are the vertices of a second equilateral triangle (refer to Problem 52). a a 2 , 23a 2 b s s s
  • 39. 8 CHAPTER 1 Graphs 65. Drafting Error When a draftsman draws three lines that are to intersect at one point, the lines may not intersect as intended and subsequently will form an error triangle. If this error triangle is long and thin, one estimate for the location of the desired point is the midpoint of the shortest side.The figure shows one such error triangle. Source: www.uwgb.edu/dutchs/STRUCTGE/sl00.htm In Problems 55–58, find the length of each side of the triangle determined by the three points and . State whether the triangle is an isosceles triangle, a right triangle, neither of these, or both. (An isosceles triangle is one in which at least two of the sides are of equal length.) P3P1, P2, 55. 56. 57. 58. 59. Baseball A major league baseball “diamond” is actually a square, 90 feet on a side (see the figure).What is the distance directly from home plate to second base (the diagonal of the square)? P1 = 17, 22; P2 = 1-4, 02; P3 = 14, 62 P1 = 1-2, -12; P2 = 10, 72; P3 = 13, 22 P1 = 1-1, 42; P2 = 16, 22; P3 = 14, -52 P1 = 12, 12; P2 = 1-4, 12; P3 = 1-4, -32 Pitching rubber Home plate 1st base 2nd base 3rd base 90 ft 90 ft 60. Little League Baseball The layout of a Little League playing field is a square, 60 feet on a side. How far is it directly from home plate to second base (the diagonal of the square)? Source: Little League Baseball, Official Regulations and Playing Rules, 2010. 61. Baseball Refer to Problem 59. Overlay a rectangular coordinate system on a major league baseball diamond so that the origin is at home plate, the positive x-axis lies in the direction from home plate to first base, and the positive y-axis lies in the direction from home plate to third base. (a) What are the coordinates of first base, second base, and third base? Use feet as the unit of measurement. (b) If the right fielder is located at how far is it from the right fielder to second base? (c) If the center fielder is located at how far is it from the center fielder to third base? 62. Little League Baseball Refer to Problem 60. Overlay a rectangular coordinate system on a Little League baseball diamond so that the origin is at home plate, the positive x-axis lies in the direction from home plate to first base, and the positive y-axis lies in the direction from home plate to third base. (a) What are the coordinates of first base, second base, and third base? Use feet as the unit of measurement. (b) If the right fielder is located at how far is it from the right fielder to second base? (c) If the center fielder is located at , how far is it from the center fielder to third base? 63. Distance between Moving Objects A Dodge Neon and a Mack truck leave an intersection at the same time.The Neon heads east at an average speed of 30 miles per hour, while the truck heads south at an average speed of 40 miles per hour. Find an expression for their distance apart d (in miles) at the end of t hours. 1220, 2202 1180, 202, 1300, 3002, 1310, 152, 15 mph East 100 ft x y (1.4, 1.3) (2.7, 1.7) (2.6, 1.5) 1.7 1.5 1.3 2.6 2.71.4 Wal-Mart Stores, Inc. Net sales (in $ billions) 2002 2004 375 204 2003 Year 2005 2006 2007 2008 350 300 250 200 Netsales($billions) 150 50 0 100 64. Distance of a Moving Object from a Fixed Point A hot-air balloon, headed due east at an average speed of 15 miles per hour and at a constant altitude of 100 feet, passes over an intersection (see the figure).Find an expression for the distance d (measured in feet) from the balloon to the intersection t seconds later. (a) Find an estimate for the desired intersection point. (b) Find the length of the median for the midpoint found in part (a). See Problem 51. 66. Net Sales The figure illustrates how net sales of Wal-Mart Stores, Inc., have grown from 2002 through 2008. Use the midpoint formula to estimate the net sales of Wal-Mart Stores, Inc., in 2005. How does your result compare to the reported value of $282 billion? Source: Wal-Mart Stores, Inc., 2008 Annual Report
  • 40. SECTION 1.2 Graphs of Equations in Two Variables;Intercepts;Symmetry 9 68. Write a paragraph that describes a Cartesian plane. Then write a second paragraph that describes how to plot points in the Cartesian plane. Your paragraphs should include the terms “coordinate axes,” “ordered pair,” “coordinates,” “plot,”“x-coordinate,” and “y-coordinate.” Explaining Concepts: Discussion and Writing 1. 0 2. 8 3. 5 4. 5. 6. TrueA = 1 2 bh112 + 602 = 121 + 3600 = 3721 = 612 ‘Are You Prepared?’Answers Now Work the ‘Are You Prepared?’ problems on page 16. OBJECTIVES 1 Graph Equations by Plotting Points (p.9) 2 Find Intercepts from a Graph (p.11) 3 Find Intercepts from an Equation (p.12) 4 Test an Equation for Symmetry with Respect to the x-Axis,the y-Axis, and the Origin (p.12) 5 Know How to Graph Key Equations (p.15) 1.2 Graphs of Equations in Two Variables; Intercepts; Symmetry • Solving Equations (Appendix A, Section A.6, pp.A44–A48) PREPARING FOR THIS SECTION Before getting started, review the following: 1 Graph Equations by Plotting Points An equation in two variables, say x and y, is a statement in which two expressions involving x and y are equal. The expressions are called the sides of the equation. Since an equation is a statement, it may be true or false, depending on the value of the variables.Any values of x and y that result in a true statement are said to satisfy the equation. For example, the following are all equations in two variables x and y: The first of these, is satisfied for since Other choices of x and y, such as , also satisfy this equation. It is not satisfied for and , since . The graph of an equation in two variables x and y consists of the set of points in the xy-plane whose coordinates satisfy the equation. Graphs play an important role in helping us to visualize the relationships that exist between two variables or quantities. Figure 11 on page 10 shows the relation between the level of risk in a stock portfolio and the average annual rate of return. From the graph, we can see that, when 30% of a portfolio of stocks is invested in foreign companies, risk is minimized. 1x, y2 22 + 32 = 4 + 9 = 13 Z 5y = 3x = 2 y = -2x = -1,1 + 4 = 5. 12 + 22 =x = 1, y = 2,x2 + y2 = 5, x2 + y2 = 5 2x - y = 6 y = 2x + 5 x2 = y 67. Poverty Threshold Poverty thresholds are determined by the U.S. Census Bureau.A poverty threshold represents the minimum annual household income for a family not to be considered poor. In 1998, the poverty threshold for a family of four with two children under the age of 18 years was $16,530. In 2008, the poverty threshold for a family of four with two children under the age of 18 years was $21,834. Assuming poverty thresholds increase in a straight-line fashion, use the midpoint formula to estimate the poverty threshold of a family of four with two children under the age of 18 in 2003. How does your result compare to the actual poverty threshold in 2003 of $18,660? Source: U.S. Census Bureau
  • 41. 10 CHAPTER 1 Graphs 18.5 18.5 19.5 17.5 17.5 16.5 16.5 15.5 15.5 14.5 14.5 13.5 13.5 18 18 19 20 17 17 16 16 15 15 14 14 AverageAnnualReturns(%) Level of Risk (%) 10% 40% 50% 30% 60% 70% (30% foreign/70% U.S.) (100% U.S.)0% 80% 90% 100% (100% foreign) 20% Figure 11 Source: T. Rowe Price Determining Whether a Point Is on the Graph of an Equation Determine if the following points are on the graph of the equation . (a) (b) 12, -2212, 32 2x - y = 6 EXAMPLE 1 Solution (a) For the point , check to see if satisfies the equation . The equation is not satisfied,so the point is not on the graph of (b) For the point , The equation is satisfied, so the point is on the graph of . Now Work P R O B L E M 1 1 2x - y = 612, -22 2x - y = 2122 - 1-22 = 4 + 2 = 6 12, -22 2x - y = 6.12, 32 2x - y = 2122 - 3 = 4 - 3 = 1 Z 6 2x - y = 6 x = 2, y = 312, 32 ᭹ Graphing an Equation by Plotting Points Graph the equation: y = 2x + 5 EXAMPLE 2 Solution We want to find all points that satisfy the equation. To locate some of these points (and get an idea of the pattern of the graph), assign some numbers to x and find corresponding values for y. 1x, y2 x y (10, 25)25 (1, 7) (0, 5) (–5, –5) 25–25 –25 Figure 12 By plotting these points and then connecting them, we obtain the graph of the equation (a line), as shown in Figure 12. ᭹ Graphing an Equation by Plotting Points Graph the equation: y = x2 EXAMPLE 3 Solution Table 1 provides several points on the graph. In Figure 13 we plot these points and connect them with a smooth curve to obtain the graph (a parabola). If Then Point on Graph 110, 252y = 21102 + 5 = 25x = 10 1-5, -52y = 21-52 + 5 = -5x = -5 11, 72y = 2112 + 5 = 7x = 1 10, 52y = 2102 + 5 = 5x = 0
  • 42. SECTION 1.2 Graphs of Equations in Two Variables;Intercepts; Symmetry 11 The graphs of the equations shown in Figures 12 and 13 do not show all points. For example, in Figure 12, the point is a part of the graph of , but it is not shown. Since the graph of could be extended out as far as we please, we use arrows to indicate that the pattern shown continues. It is important when illustrating a graph to present enough of the graph so that any viewer of the illustration will “see” the rest of it as an obvious continuation of what is actually there.This is referred to as a complete graph. One way to obtain a complete graph of an equation is to plot a sufficient number of points on the graph until a pattern becomes evident. Then these points are connected with a smooth curve following the suggested pattern. But how many points are sufficient? Sometimes knowledge about the equation tells us. For example, we will learn in the next section that, if an equation is of the form , then its graph is a line. In this case, only two points are needed to obtain the graph. One purpose of this book is to investigate the properties of equations in order to decide whether a graph is complete. Sometimes we shall graph equations by plotting points. Shortly, we shall investigate various techniques that will enable us to graph an equation without plotting so many points. y = mx + b y = 2x + 5 y = 2x + 5120, 452 Table 1 x y –4 4 (4, 16)(–4, 16) (3, 9)(–3, 9) (2, 4)(–2, 4) (1, 1) (0, 0) (–1, 1) 5 10 15 20 Figure 13 x 16 9 4 1 0 0 (0,0) 1 1 (1,1) 2 4 (2,4) 3 9 (3,9) 4 16 (4,16) (-1, 1)-1 (-2, 4)-2 (-3, 9)-3 (-4, 16)-4 (x, y)y ‫؍‬ x2 ᭹ COMMENT Another way to obtain the graph of an equation is to use a graphing utility. Read Section B.2, Using a Graphing Utility to Graph Equations, in Appendix B. ᭿ Two techniques that sometimes reduce the number of points required to graph an equation involve finding intercepts and checking for symmetry. 2 Find Intercepts from a Graph The points, if any, at which a graph crosses or touches the coordinate axes are called the intercepts. See Figure 14.The x-coordinate of a point at which the graph crosses or touches the x-axis is an x-intercept, and the y-coordinate of a point at which the graph crosses or touches the y-axis is a y-intercept. For a graph to be complete, all its intercepts must be displayed. x y Intercepts Graph touches x-axis Graph crosses x-axis Graph crosses y-axis Figure 14 In Example 4,you should notice the following usage:If we do not specify the type of intercept (x- versus y-), then report the intercept as an ordered pair. However, if the type of intercept is specified, then report the coordinate of the specified intercept. For x-intercepts, report the x-coordinate of the intercept; for y-intercepts, report the y-coordinate of the intercept. Now Work P R O B L E M 3 9 ( a ) Solution The intercepts of the graph are the points The x-intercepts are , and 4.5; the y-intercepts are , and 3.- 4 3 ,-3.5 3 2 ,-3 1-3, 02, 10, 32, a 3 2 , 0b, a0, - 4 3 b, 10, -3.52, 14.5, 02 Finding Intercepts from a Graph Find the intercepts of the graph in Figure 15.What are its x-intercepts? What are its y-intercepts? EXAMPLE 4 ᭹ x y (0, 3) (Ϫ3, 0) , 0( ) (0, Ϫ )4 – 3 3– 2 (4.5, 0) (0, Ϫ3.5) 4 Ϫ4 5 Figure 15
  • 43. 12 CHAPTER 1 Graphs 3 Find Intercepts from an Equation The intercepts of a graph can be found from its equation by using the fact that points on the x-axis have y-coordinates equal to 0 and points on the y-axis have x-coordinates equal to 0. Procedure for Finding Intercepts 1. To find the x-intercept(s), if any, of the graph of an equation, let in the equation and solve for x, where x is a real number. 2. To find the y-intercept(s), if any, of the graph of an equation, let in the equation and solve for y, where y is a real number. x = 0 y = 0 Finding Intercepts from an Equation Find the x-intercept(s) and the y-intercept(s) of the graph of . Then graph by plotting points.y = x2 - 4 y = x2 - 4 EXAMPLE 5 COMMENT For many equations, finding intercepts may not be so easy. In such cases, a graphing utility can be used. Read the first part of Section B.3, Using a Graphing Utility to Locate In- tercepts and Check for Symmetry, in Appendix B, to find out how to locate intercepts using a graphing utility. ᭿ Solution To find the x-intercept(s), let and obtain the equation or or The equation has two solutions, and 2.The x-intercepts are and 2. To find the y-intercept(s), let in the equation. The y-intercept is . Since for all x, we deduce from the equation that for all x.This information, the intercepts, and the points from Table 2 enable us to graph . See Figure 16.y = x2 - 4 y Ú -4y = x2 - 4x2 Ú 0 -4 = 02 - 4 = -4 y = x2 - 4 x = 0 -2-2 Solve.x = 2x = -2 Zero-Product Propertyx - 2 = 0x + 2 = 0 Factor.1x + 221x - 2) = 0 y = x2 - 4 with y = 0x2 - 4 = 0 y = 0 x y (3, 5)5 (2, 0) (–1, –3) (1, –3) (0, –4) (–3, 5) (–2, 0) 5–5 –5 Figure 16Table 2 x 5 1 3 5 (3, 5) (1, -3)-3 (-1, -3)-3-1 (-3, 5)-3 (x, y)y ‫؍‬ x2 ؊ 4 Now Work P R O B L E M 2 1 ᭹ 4 Test an Equation for Symmetry with Respect to the x-Axis,the y-Axis,and the Origin We just saw the role that intercepts play in obtaining key points on the graph of an equation.Another helpful tool for graphing equations involves symmetry, particularly symmetry with respect to the x-axis, the y-axis, and the origin. DEFINITION A graph is said to be symmetric with respect to the x-axis if, for every point on the graph, the point is also on the graph.1x, -y21x, y2
  • 44. SECTION 1.2 Graphs of Equations in Two Variables;Intercepts; Symmetry 13 Figure 17 illustrates the definition. When a graph is symmetric with respect to the x-axis, notice that the part of the graph above the x-axis is a reflection or mirror image of the part below it, and vice versa. Points Symmetric with Respect to the x-Axis If a graph is symmetric with respect to the x-axis and the point is on the graph, then the point is also on the graph.13, -22 13, 22 EXAMPLE 6 ᭹ DEFINITION A graph is said to be symmetric with respect to the y-axis if, for every point on the graph, the point is also on the graph.1-x, y21x, y2 Figure 18 illustrates the definition. When a graph is symmetric with respect to the y-axis, notice that the part of the graph to the right of the y-axis is a reflection of the part to the left of it, and vice versa. Points Symmetric with Respect to the y-Axis If a graph is symmetric with respect to the y-axis and the point is on the graph, then the point is also on the graph.1-5, 82 15, 82 EXAMPLE 7 ᭹ (x, –y) (x, y) (x, –y) (x, y) (x, y) (x, –y) x yFigure 17 Symmetry with respect to the x-axis (–x, y) (–x, y) (x, y) (x, y) x y Figure 18 Symmetry with respect to the y-axis DEFINITION A graph is said to be symmetric with respect to the origin if, for every point on the graph, the point is also on the graph.1-x, -y21x, y2 Figure 19 illustrates the definition. Notice that symmetry with respect to the origin may be viewed in three ways: 1. As a reflection about the y-axis, followed by a reflection about the x-axis 2. As a projection along a line through the origin so that the distances from the origin are equal 3. As half of a complete revolution about the origin (x, y) (x, y) (–x, –y) (–x, –y) x y Figure 19 Symmetry with respect to the origin Points Symmetric with Respect to the Origin If a graph is symmetric with respect to the origin and the point 4, 2 is on the graph, then the point is also on the graph. Now Work P R O B L E M S 2 9 A N D 3 9 ( b ) When the graph of an equation is symmetric with respect to a coordinate axis or the origin, the number of points that you need to plot in order to see the pattern is reduced. For example, if the graph of an equation is symmetric with respect to the y-axis, then, once points to the right of the y-axis are plotted, an equal number of points on the graph can be obtained by reflecting them about the y-axis. Because of this, before we graph an equation, we first want to determine whether it has any symmetry.The following tests are used for this purpose. 1-4, -22 21 EXAMPLE 8 ᭹
  • 45. 14 CHAPTER 1 Graphs Testing an Equation for Symmetry Test for symmetry.y = 4x2 x2 + 1 EXAMPLE 9 Solution x-Axis: To test for symmetry with respect to the x-axis, replace y by . Since is not equivalent to the graph of the equation is not symmetric with respect to the x-axis. y-Axis: To test for symmetry with respect to the y-axis, replace x by . Since is equivalent to the graph of the equation is symmetric with respect to the y-axis. Origin: To test for symmetry with respect to the origin, replace x by and y by . Replace x by and y by Simplify. Multiply both sides by Since the result is not equivalent to the original equation, the graph of the equation is not symmetric with respect to the origin. Seeing the Concept Figure 20 shows the graph of using a graphing utility. Do you see the symmetry with respect to the y-axis? y = 4x2 x2 + 1 y = 4x2 x2 + 1 -1.y = - 4x2 x2 + 1 -y = 4x2 x2 + 1 -y.-x-y = 41-x22 1-x22 + 1 -y-x y = 4x2 x2 + 1 ,y = 41-x22 1-x22 + 1 = 4x2 x2 + 1 -x y = 4x2 x2 + 1 ,-y = 4x2 x2 + 1 -y ᭹ Tests for Symmetry To test the graph of an equation for symmetry with respect to the x-Axis Replace y by Ϫy in the equation and simplify. If an equivalent equation results, the graph of the equation is symmetric with respect to the x-axis. y-Axis Replace x by Ϫx in the equation and simplify. If an equivalent equation results, the graph of the equation is symmetric with respect to the y-axis. Origin Replace x by Ϫx and y by Ϫy in the equation and simplify. If an equivalent equation results, the graph of the equation is symmetric with respect to the origin. 5 Ϫ5 Ϫ5 5 Figure 20 Now Work P R O B L E M 5 9
  • 46. SECTION 1.2 Graphs of Equations in Two Variables;Intercepts; Symmetry 15 x-Axis: Replace y by . Since is not equivalent to , the graph is not symmetric with respect to the x-axis. y-Axis: Replace x by . Since is not equivalent to , the graph is not symmetric with respect to the y-axis. Origin: Replace x by and y by . Since is equivalent to (multiply both sides by ), the graph is symmetric with respect to the origin. -1y = x3 -y = 1-x23 = -x3 -y-x y = x3 y = 1-x23 = -x3 -x y = x3 -y = x3 -y 5 Know How to Graph Key Equations The next three examples use intercepts, symmetry, and point plotting to obtain the graphs of key equations. It is important to know the graphs of these key equations because we use them later.The first of these is .y = x3 Graphing the Equation y ‫؍‬ x3 by Finding Intercepts, Checking for Symmetry, and Plotting Points Graph the equation by plotting points. Find any intercepts and check for symmetry first. y = x3 EXAMPLE 10 Solution First, find the intercepts. When , then ; and when , then . The origin is the only intercept. Now test for symmetry.10, 02 x = 0y = 0y = 0x = 0 To graph , we use the equation to obtain several points on the graph. Because of the symmetry, we only need to locate points on the graph for which . See Table 3. Since 1, 1 is on the graph, and the graph is symmetric with respect to the origin, the point is also on the graph. Plot the points from Table 3 and use the symmetry. Figure 21 shows the graph. 1-1, -12 21x Ú 0 y = x3 x y (2, 8)8 (1, 1)(0, 0) (–1, –1) 6–6 –8(–2, –8) Figure 21 Table 3 x 0 0 1 1 2 8 (2,8) 3 27 (3,27) (1, 1) (0, 0) (x, y)y ‫؍‬ x3 ᭹ Graphing the Equation x ‫؍‬ y2 (a) Graph the equation . Find any intercepts and check for symmetry first. (b) Graph x = y2 , y Ú 0. x = y2 EXAMPLE 11 x y (9, 3) 6 (4, 2) (0, 0) (1, –1) 10–2 (9, –3) 5 (1, 1) (4, –2) Figure 22 x = y2 x y (9, 3) 6 (4, 2) (0, 0) 10–2 5 (1, 1) Figure 23 y = 2x Y1 ϭ 6 Ϫ6 Ϫ2 10 x Y2 ϭ Ϫ x Figure 24 Solution (a) The lone intercept is . The graph is symmetric with respect to the x-axis. (Do you see why? Replace y by .) Figure 22 shows the graph. (b) If we restrict y so that , the equation , , may be written equivalently as . The portion of the graph of in quadrant I is therefore the graph of See Figure 23.y = 1x. x = y2 y = 1x y Ú 0x = y2 y Ú 0 -y 10, 02 COMMENT To see the graph of the equation on a graphing calculator, you will need to graph two equations: and We discuss why in Chapter 2. See Figure 24. ᭿Y2 = - 1x.Y1 = 1x x = y2 ᭹
  • 47. 16 CHAPTER 1 Graphs Graphing the Equation Graph the equation Find any intercepts and check for symmetry first.y = 1 x . y ‫؍‬ 1 x EXAMPLE 12 Solution Check for intercepts first. If we let , we obtain 0 in the denominator, which makes y undefined.We conclude that there is no y-intercept. If we let , we get the equation , which has no solution.We conclude that there is no x-intercept. The graph of does not cross or touch the coordinate axes. Next check for symmetry: x-Axis: Replacing y by yields which is not equivalent to y-Axis: Replacing x by yields , which is not equivalent to Origin: Replacing x by and y by yields which is equivalent to The graph is symmetric with respect to the origin. Now, set up Table 4, listing several points on the graph. Because of the symmetry with respect to the origin, we use only positive values of x. From Table 4 we infer that if x is a large and positive number, then is a positive number close to 0.We also infer that if x is a positive number close to 0, then is a large and positive number.Armed with this information, we can graph the equation. Figure 25 illustrates some of these points and the graph of Observe how the absence of intercepts and the existence of symmetry with respect to the origin were utilized. y = 1 x . y = 1 x y = 1 x y = 1 x . -y = - 1 x ,-y-x y = 1 x . y = 1 -x = - 1 x -x y = 1 x .-y = 1 x ,-y y = 1 x 1 x = 0 y = 0 x = 0Table 4 x 10 3 2 1 1 2 3 10 a10, 1 10 b 1 10 a3, 1 3 b 1 3 a2, 1 2 b 1 2 (1, 1) a 1 2 , 2b 1 2 a 1 3 , 3b 1 3 a 1 10 , 10b 1 10 (x, y)y ‫؍‬ 1 x x y 3 3 –3 –3 , 2 – 1–– 2 (1, 1) 2, 1–– 2 –2,( ) ( ) ( ) ( ) 1–– 2 (–1, –1) , –21–– 2 – Figure 25 COMMENT Refer to Example 2 in Appendix B, Section B.3, for the graph of using a graphing utility. ᭿ y = 1 x ᭹ ‘Are You Prepared?’ Answers are given at the end of these exercises. If you get a wrong answer, read the pages listed in red. 1. Solve the equation . (pp.A44–A48)21x + 32 - 1 = -7 2. Solve the equation . (pp.A44–A48)x2 - 9 = 0 1.2 Assess Your Understanding 3. The points, if any, at which a graph crosses or touches the coordinate axes are called . 4. The x-intercepts of the graph of an equation are those x-values for which . 5. If for every point on the graph of an equation the point is also on the graph, then the graph is symmetric with respect to the . 6. If the graph of an equation is symmetric with respect to the y-axis and is an x-intercept of this graph, then is also an x-intercept. -4 1-x, y2 1x, y2 7. If the graph of an equation is symmetric with respect to the origin and is a point on the graph, then is also a point on the graph. 8. True or False To find the y-intercepts of the graph of an equation, let and solve for y. 9. True or False The y-coordinate of a point at which the graph crosses or touches the x-axis is an x-intercept. 10. True or False If a graph is symmetric with respect to the x-axis, then it cannot be symmetric with respect to the y-axis. x = 0 13, -42 Concepts and Vocabulary
  • 48. SECTION 1.2 Graphs of Equations in Two Variables;Intercepts; Symmetry 17 In Problems 17–28, find the intercepts and graph each equation by plotting points. Be sure to label the intercepts. Skill Building In Problems 11–16, determine which of the given points are on the graph of the equation. 11. Equation: Points: 10, 02; 11, 12; 1-1, 02 y = x4 - 1x 12. Equation: Points: 10, 02; 11, 12; 11, -12 y = x3 - 21x 13. Equation: Points: 10, 32; 13, 02; 1-3, 02 y2 = x2 + 9 14. Equation: Points: 11, 22; 10, 12; 1-1, 02 y3 = x + 1 15. Equation: Points: 10, 22; 1-2, 22; A 22, 22B x2 + y2 = 4 16. Equation: Points: 10, 12; 12, 02; a2, 1 2 b x2 + 4y2 = 4 17. y = x + 2 18. y = x - 6 19. y = 2x + 8 20. y = 3x - 9 21. y = x2 - 1 22. y = x2 - 9 23. y = -x2 + 4 24. y = -x2 + 1 25. 2x + 3y = 6 26. 5x + 2y = 10 27. 9x2 + 4y = 36 28. 4x2 + y = 4 In Problems 29–38, plot each point.Then plot the point that is symmetric to it with respect to (a) the x-axis; (b) the y-axis; (c) the origin. 29. 13, 42 30. 15, 32 31. 1-2, 12 32. 14, -22 33. 15, -22 34. 1-1, -12 35. 1-3, -42 36. 14, 02 37. 10, -32 38. 1-3, 02 In Problems 39–50, the graph of an equation is given. (a) Find the intercepts. (b) Indicate whether the graph is symmetric with respect to the x-axis, the y-axis, or the origin. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. In Problems 51–54, draw a complete graph so that it has the type of symmetry indicated. 51. y-axis 52. x-axis 53. Origin 54. y-axis x y 3 3–3 –3 x y 3 3 –3 –3 y 6 Ϫ6 x3Ϫ3 40 Ϫ40 x 6Ϫ6 y 3 –3 x y 3 –3 3 Ϫ3 x y 3 Ϫ3 x y ␲ 1 Ϫ1 Ϫ␲ ␲–– 2 Ϫ ␲–– 2 x y 3 4 Ϫ4 Ϫ3 y 3 Ϫ3 x3Ϫ3 y 3 Ϫ3 x3Ϫ3 Ϫ8 8 Ϫ2 2 Ϫ4 4 Ϫ4 4 9–9 –9 9 x y (0, –9) (2, –5) x y –5 5 –5 5 (–4, 0) (0, 2) (5, 3) x y –4 4 ␲–– 2 (␲, 0) (0, 0) ( , 2) y –3 3 –2 4 (0, 4) (0, 0) (2, 2) x
  • 49. 18 CHAPTER 1 Graphs In Problems 55–70, list the intercepts and test for symmetry. 55. y2 = x + 4 56. y2 = x + 9 57. y = 1 3 x 58. y = 15 x 59. x2 + y - 9 = 0 60. x2 - y - 4 = 0 61. 9x2 + 4y2 = 36 62. 4x2 + y2 = 4 63. y = x3 - 27 64. y = x4 - 1 65. y = x2 - 3x - 4 66. y = x2 + 4 67. y = 3x x2 + 9 68. y = x2 - 4 2x 69. y = -x3 x2 - 9 70. y = x4 + 1 2x5 In Problems 71–74, draw a quick sketch of each equation. 71. y = x3 72. x = y2 73. y = 1x 74. y = 1 x 75. If is a point on the graph of , what is b?y = 4x + 113, b2 76. If is a point on the graph of , what is b?2x + 3y = 21-2, b2 77. If is a point on the graph of , what is a?y = x2 + 3x1a, 42 78. If is a point on the graph of , what is a?y = x2 + 6x1a, -52 79. Given that the point (1, 2) is on the graph of an equation that is symmetric with respect to the origin, what other point is on the graph? 80. If the graph of an equation is symmetric with respect to the y-axis and 6 is an x-intercept of this graph, name another x-intercept. 81. If the graph of an equation is symmetric with respect to the origin and is an x-intercept of this graph, name another x-intercept. 82. If the graph of an equation is symmetric with respect to the x-axis and 2 is a y-intercept, name another y-intercept. 83. Microphones In studios and on stages, cardioid micro- phones are often preferred for the richness they add to voices and for their ability to reduce the level of sound from the sides and rear of the microphone. Suppose one such cardioid pattern is given by the equation (a) Find the intercepts of the graph of the equation. (b) Test for symmetry with respect to the x-axis, y-axis, and origin. Source: www.notaviva.com 1x2 + y2 - x22 = x2 + y2 . -4 84. Solar Energy The solar electric generating systems at Kramer Junction, California, use parabolic troughs to heat a heat-transfer fluid to a high temperature. This fluid is used to generate steam that drives a power conversion system to produce electricity. For troughs 7.5 feet wide, an equation for the cross-section is .16y2 = 120x - 225 Applications and Extensions (a) Find the intercepts of the graph of the equation. (b) Test for symmetry with respect to the x-axis, y-axis, and origin. Source: U.S. Department of Energy 85. (a) Graph , and , noting which graphs are the same. (b) Explain why the graphs of and are the same. (c) Explain why the graphs of and are not the same. (d) Explain why the graphs of and are not the same. 86. Explain what is meant by a complete graph. 87. Draw a graph of an equation that contains two x-intercepts; at one the graph crosses the x-axis, and at the other the graph touches the x-axis. 88. Make up an equation with the intercepts , and . Compare your equation with a friend’s equation. Comment on any similarities. 10, 12 12, 02, 14, 02 y = xy = 3x2 y = 11x22 y = x y = ƒxƒy = 3x2 y = 11x22 y = 3x2 , y = x, y = ƒxƒ 89. Draw a graph that contains the points , and . Compare your graph with those of other students.Are most of the graphs almost straight lines? How many are “curved”? Discuss the various ways that these points might be connected. 90. An equation is being tested for symmetry with respect to the x-axis, the y-axis, and the origin. Explain why, if two of these symmetries are present, the remaining one must also be present. 91. Draw a graph that contains the points , , and (0, 2) that is symmetric with respect to the y-axis. Compare your graph with those of other students; comment on any similarities. Can a graph contain these points and be symmetric with respect to the x-axis? the origin? Why or why not? (-1, 3)(-2, 5) 13, 5211, 32 10, 12,1-2, -12, Explaining Concepts: Discussion and Writing
  • 50. SECTION 1.3 Lines 19 In this section we study a certain type of equation that contains two variables, called a linear equation, and its graph, a line. Rise Line Run Figure 26 1.3 Lines OBJECTIVES 1 Calculate and Interpret the Slope of a Line (p.19) 2 Graph Lines Given a Point and the Slope (p.22) 3 Find the Equation of a Vertical Line (p.22) 4 Use the Point–Slope Form of a Line;Identify Horizontal Lines (p.23) 5 Find the Equation of a Line Given Two Points (p.24) 6 Write the Equation of a Line in Slope–Intercept Form (p.24) 7 Identify the Slope and y-Intercept of a Line from Its Equation (p.25) 8 Graph Lines Written in General Form Using Intercepts (p.26) 9 Find Equations of Parallel Lines (p.27) 10 Find Equations of Perpendicular Lines (p.28) 1 Calculate and Interpret the Slope of a Line Consider the staircase illustrated in Figure 26. Each step contains exactly the same horizontal run and the same vertical rise. The ratio of the rise to the run, called the slope, is a numerical measure of the steepness of the staircase. For example, if the run is increased and the rise remains the same, the staircase becomes less steep. If the run is kept the same, but the rise is increased, the staircase becomes more steep.This important characteristic of a line is best defined using rectangular coordinates. 92. y-axis Symmetry Open the y-axis symmetry applet. Move point A around the Cartesian plane with your mouse. How are the coordinates of pointA and the coordinates of point B related? 93. x-axis Symmetry Open the x-axis symmetry applet. Move point A around the Cartesian plane with your mouse. How are the coordinates of pointA and the coordinates of point B related? 94. Origin Symmetry Open the origin symmetry applet. Move point A around the Cartesian plane with your mouse. How are the coordinates of pointA and the coordinates of point B related? Interactive Exercises Ask your instructor if the applets below are of interest to you. 1. 2. 5- 3, 365-66 ‘Are You Prepared?’Answers DEFINITION Let and be two distinct points.If the slope m of the nonvertical line L containing P and Q is defined by the formula (1) If L is a vertical line and the slope m of L is undefined (since this results in division by 0). x1 = x2, m = y2 - y1 x2 - x1 x1 Z x2 x1 Z x2,Q = 1x2, y22P = 1x1, y12 Figure 27(a) on page 20 provides an illustration of the slope of a nonvertical line; Figure 27(b) illustrates a vertical line.
  • 51. Finding and Interpreting the Slope of a Line Given Two Points The slope m of the line containing the points and may be computed as For every 4-unit change in x, y will change by . That is, if x increases by 4 units, then y will decrease by 5 units. The average rate of change of y with respect to x is Now Work P R O B L E M S 1 1 A N D 1 7 - 5 4 . -5 units m = -3 - 2 5 - 1 = -5 4 = - 5 4 or as m = 2 - 1-32 1 - 5 = 5 -4 = - 5 4 15, -3211, 22 EXAMPLE 1 ᭹ 20 CHAPTER 1 Graphs Rise = y2 – y1 Q = (x2, y2) P = (x1 , y1 ) L Run = x2 – x1 Slope of L is m =(a) x1 x2 y2 y1 y2 – y1_______ x2 – x1 Q = (x1, y2) P = (x1, y1) L Slope is undefined; L is vertical(b) x1 y2 y1 Figure 27 As Figure 27(a) illustrates, the slope m of a nonvertical line may be viewed as m = y2 - y1 x2 - x1 = Rise Run or m = y2 - y1 x2 - x1 = Change in y Change in x = ¢y ¢x That is, the slope m of a nonvertical line measures the amount y changes when x changes from to . The expression is called the average rate of change of y, with respect to x. Two comments about computing the slope of a nonvertical line may prove helpful: 1. Any two distinct points on the line can be used to compute the slope of the line. (See Figure 28 for justification.) ¢y ¢x x2x1 x y R A C B y2 – y1 Q = (x2, y2) P = (x1 , y1 ) x2 – x1 Figure 28 Triangles ABC and PQR are similar (equal angles),so ratios of corresponding sides are proportional. Then d(B, C) d(A, C) = Slope using A and B Slope using P and Q = y2 - y1 x2 - x1 = Since any two distinct points can be used to compute the slope of a line, the average rate of change of a line is always the same number. 2. The slope of a line may be computed from to or from Q to P because y2 - y1 x2 - x1 = y1 - y2 x1 - x2 Q = 1x2, y22P = 1x1, y12
  • 52. SECTION 1.3 Lines 21 Finding the Slopes of Various Lines Containing the Same Point (2, 3) Compute the slopes of the lines and containing the following pairs of points. Graph all four lines on the same set of coordinate axes. L4: P = 12, 32 Q4 = 12, 52 L3: P = 12, 32 Q3 = 15, 32 L2: P = 12, 32 Q2 = 13, -12 L1: P = 12, 32 Q1 = 1-1, -22 L4L3,L2,L1, EXAMPLE 2 Solution Let and denote the slopes of the lines and respectively. Then A rise of 5 divided by a run of 3 The graphs of these lines are given in Figure 29. Figure 29 illustrates the following facts: m4 is undefined because x1 = x2 = 2 m3 = 3 - 3 5 - 2 = 0 3 = 0 m2 = -1 - 3 3 - 2 = -4 1 = -4 m1 = -2 - 3 -1 - 2 = -5 -3 = 5 3 L4,L3,L2,L1,m4m1, m2, m3, x y Ϫ5 5 5 Ϫ3 Q4 ϭ (2, 5) Q1 ϭ (Ϫ1, Ϫ2) m1 ϭ m2 ϭ Ϫ4 m4 undefined m3 ϭ 0m3 ϭ 0 L4 Q3 ϭ (5, 3) Q2 ϭ (3, Ϫ1) P ϭ (2, 3) 5– 3 L3L3 L2 L1 Figure 29 ᭹ 1. When the slope of a line is positive, the line slants upward from left to right . 2. When the slope of a line is negative, the line slants downward from left to right . 3. When the slope is 0, the line is horizontal . 4. When the slope is undefined, the line is vertical .1L42 1L32 1L22 1L12 Seeing the Concept On the same screen,graph the following equations: Slope of line is 0. Slope of line is Slope of line is Slope of line is 1. Slope of line is 2. Slope of line is 6. See Figure 30. Y6 = 6x Y5 = 2x Y4 = x 1 2 .Y3 = 1 2 x 1 4 .Y2 = 1 4 x Y1 = 0 Ϫ2 2 1 4 Y6 ϭ 6x Y5 ϭ 2x Y4 ϭ x Y3 ϭ x Y2 ϭ x Y1 ϭ 0 Ϫ3 3 1 2 Figure 30 Ϫ2 2 1 4 Y6 ϭ Ϫ6x Y5 ϭ Ϫ2x Y4 ϭ Ϫx Y3 ϭ Ϫ x Y2 ϭ Ϫ x Y1 ϭ 0 Ϫ3 3 1 2 Figure 31 Seeing the Concept On the same screen,graph the following equations: Slope of line is 0. Slope of line is Slope of line is Slope of line is -1. Slope of line is -2. Slope of line is -6. See Figure 31. Y6 = -6x Y5 = -2x Y4 = -x - 1 2 .Y3 = - 1 2 x - 1 4 .Y2 = - 1 4 x Y1 = 0
  • 53. 3 Find the Equation of a Vertical Line Graphing a Line Graph the equation: x = 3 EXAMPLE 4 Solution To graph , we find all points in the plane for which . No matter what y-coordinate is used, the corresponding x-coordinate always equals 3. Consequently,the graph of the equation is a vertical line with x-intercept 3 and undefined slope. See Figure 34. x = 3 x = 31x, y2x = 3 x y 5Ϫ1 (3, 3) (3, 2) (3, 1) (3, 0) (3, Ϫ1) 4 Ϫ1 Figure 34 ᭹ 22 CHAPTER 1 Graphs 2 Graph Lines Given a Point and the Slope Graphing a Line Given a Point and a Slope Draw a graph of the line that contains the point and has a slope of: (a) (b) - 4 5 3 4 13, 22 EXAMPLE 3 Solution (a) The fact that the slope is means that for every horizontal movement (run) of 4 units to the right there will be a vertical movement (rise) of 3 units. Look at Figure 32. If we start at the given point and move 4 units to the right and 3 units up, we reach the point . By drawing the line through this point and the point , we have the graph. (b) The fact that the slope is means that for every horizontal movement of 5 units to the right there will be a corresponding vertical movement of units (a downward movement). If we start at the given point and move 5 units to the right and then 4 units down, we arrive at the point . By drawing the line through these points, we have the graph. See Figure 33. Alternatively, we can set so that for every horizontal movement of units (a movement to the left) there will be a corresponding vertical movement of 4 units (upward). This approach brings us to the point , which is also on the graph shown in Figure 33. Now Work P R O B L E M 2 3 1-2, 62 -5 - 4 5 = 4 -5 = Rise Run 18, -22 13, 22 -4 - 4 5 = -4 5 = Rise Run 13, 22 17, 52 13, 22 3 4 Slope = Rise Run . x y –2 10 Rise = 3 Run = 4 (7, 5) (3, 2) 5 6 Figure 32 x y –2 10 (8, –2) (–2, 6) (3, 2) 6 –2 Run = 5 Run = –5 Rise=4 Rise = –4 Figure 33 ᭹ Figures 30 and 31 on page 21 illustrate that the closer the line is to the vertical position, the greater the magnitude of the slope.
  • 54. SECTION 1.3 Lines 23 As suggested by Example 4, we have the following result: THEOREM Equation of a Vertical Line A vertical line is given by an equation of the form where a is the x-intercept. x = a COMMENT To graph an equation using a graphing utility, we need to express the equation in the form in But cannot be put in this form. To overcome this, most graphing utilities have special commands for drawing vertical lines. DRAW, LINE, PLOT, and VERT are among the more common ones. Consult your manual to determine the correct methodology for your graphing utility. ᭿ x = 3x6.y = 5expression x y (x, y) L (x1, y1) x – x1 y – y1 4 Use the Point–Slope Form of a Line; Identify Horizontal Lines Let L be a nonvertical line with slope m and containing the point . See Figure 35. For any other point on L, we have m = y - y1 x - x1 or y - y1 = m1x - x12 1x, y2 1x1, y12 THEOREM Point–Slope Form of an Equation of a Line An equation of a nonvertical line with slope m that contains the point is (2)y - y1 = m1x - x12 1x1, y12 Figure 35 Using the Point–Slope Form of a Line An equation of the line with slope 4 and containing the point can be found by using the point–slope form with , and . Solve for y. See Figure 36 for the graph. Now Work P R O B L E M 4 5 y = 4x - 2 m = 4, x1 = 1, y1 = 2y - 2 = 41x - 12 y - y1 = m1x - x12 y1 = 2m = 4, x1 = 1 11, 22 EXAMPLE 5 x y Ϫ2 105 (1, 2) (2, 6) 6 Run ϭ 1 Rise ϭ 4 Figure 36 ᭹ Finding the Equation of a Horizontal Line Find an equation of the horizontal line containing the point .13, 22 EXAMPLE 6 Solution Because all the y-values are equal on a horizontal line, the slope of a horizontal line is 0.To get an equation, we use the point–slope form with , and . See Figure 37 for the graph. y = 2 y - 2 = 0 m = 0, x1 = 3, and y1 = 2y - 2 = 0 # 1x - 32 y - y1 = m1x - x12 y1 = 2m = 0, x1 = 3 (3, 2) x y –1 531 4 Figure 37 ᭹
  • 55. 6 Write the Equation of a Line in Slope–Intercept Form Another useful equation of a line is obtained when the slope m and y-intercept b are known. In this event, we know both the slope m of the line and a point on the line; then we use the point–slope form, equation (2), to obtain the following equation: y - b = m1x - 02 or y = mx + b 10, b2 THEOREM Slope–Intercept Form of an Equation of a Line An equation of a line with slope m and y-intercept b is (3) Now Work P R O B L E M 5 1 ( E X P R E S S A N S W E R I N S L O P E – I N T E R C E P T F O R M ) y = mx + b In the solution to Example 7, we could have used the other point, , instead of the point . The equation that results, although it looks different, is equivalent to the equation that we obtained in the example. (Try it for yourself.) Now Work P R O B L E M 3 7 12, 32 1-4, 52 24 CHAPTER 1 Graphs THEOREM Equation of a Horizontal Line A horizontal line is given by an equation of the form where b is the y-intercept. y = b 5 Find the Equation of a Line Given Two Points Finding an Equation of a Line Given Two Points Find an equation of the line containing the points and . Graph the line.1-4, 5212, 32 EXAMPLE 7 Solution First compute the slope of the line. Use the point and the slope to get the point–slope form of the equation of the line. See Figure 38 for the graph. y - 3 = - 1 3 1x - 22 m = - 1 3 12, 32 m = 5 - 3 -4 - 2 = 2 -6 = - 1 3 ᭹ x y –4 10 (–4, 5) (2, 3) 2 –2 Figure 38 As suggested by Example 6, we have the following result:
  • 56. SECTION 1.3 Lines 25 Ϫ4 4 Y4 ϭ 3x ϩ 2Y5 ϭ Ϫ3x ϩ 2 Y3 ϭ Ϫx ϩ 2 Y2 ϭ x ϩ 2 Y1 ϭ 2 Ϫ6 6 Figure 39 y = mx + 2 Seeing the Concept To see the role of the y-intercept b,graph the following lines on the same screen. See Figure 40. What do you conclude about the lines y = 2x + b? Y5 = 2x - 4 Y4 = 2x + 4 Y3 = 2x - 1 Y2 = 2x + 1 Y1 = 2x Ϫ4 4 Y4 ϭ 2x ϩ 4 Y5 ϭ 2x Ϫ 4 Y3 ϭ 2x Ϫ 1 Y2 ϭ 2x ϩ 1 Y1 ϭ 2x Ϫ6 6 Figure 40 y = 2x + b 7 Identify the Slope and y-Intercept of a Line from Its Equation When the equation of a line is written in slope–intercept form, it is easy to find the slope m and y-intercept b of the line. For example, suppose that the equation of a line is Compare it to . The slope of this line is and its y-intercept is 7. Now Work P R O B L E M 7 1 -2 y = mx + b cc y = -2x + 7 y = mx + b y = -2x + 7 Seeing the Concept To see the role that the slope m plays,graph the following lines on the same screen. See Figure 39. What do you conclude about the lines y = mx + 2? Y5 = -3x + 2 Y4 = 3x + 2 Y3 = -x + 2 Y2 = x + 2 Y1 = 2 Finding the Slope and y-Intercept Find the slope m and y-intercept b of the equation .Graph the equation.2x + 4y = 8 EXAMPLE 8 Solution To obtain the slope and y-intercept, write the equation in slope–intercept form by solving for y. The coefficient of x, is the slope, and the y-intercept is 2. Graph the line using the fact that the y-intercept is 2 and the slope is Then, starting at the point go to the right 2 units and then down 1 unit to the point . See Figure 41. Now Work P R O B L E M 7 7 12, 1210, 22, - 1 2 . - 1 2 , y = mx + by = - 1 2 x + 2 4y = -2x + 8 2x + 4y = 8 x y –3 3 (0, 2) (2, 1) 2 1 4 Figure 41 ᭹
  • 57. The x-intercept is 4 and the point is on the graph of the equation. To obtain the y-intercept, let in the equation and solve for y. Let Divide both sides by 4. The y-intercept is 2 and the point is on the graph of the equation. Plot the points and and draw the line through the points. See Figure 42. Now Work P R O B L E M 9 1 Every line has an equation that is equivalent to an equation written in general form. For example, a vertical line whose equation is can be written in the general form A horizontal line whose equation is can be written in the general form A = 0, B = 1, C = b0 # x + 1 # y = b y = b A = 1, B = 0, C = a1 # x + 0 # y = a x = a 10, 2214, 02 10, 22 y = 2 4y = 8 x = 0.2102 + 4y = 8 2x + 4y = 8 x = 0 14, 02 x y –3 3 (0, 2) (4, 0) 4 Figure 42 ᭹ 26 CHAPTER 1 Graphs 8 Graph Lines Written in General Form Using Intercepts Refer to Example 8. The form of the equation of the line is called the general form. 2x + 4y = 8 DEFINITION The equation of a line is in general form* when it is written as (4) where A, B, and C are real numbers and A and B are not both 0. Ax + By = C If in (4), then and the graph of the equation is a vertical line: . If in (4), then we can solve the equation for y and write the equation in slope–intercept form as we did in Example 8. Another approach to graphing the equation (4) would be to find its intercepts. Remember, the intercepts of the graph of an equation are the points where the graph crosses or touches a coordinate axis. B Z 0x = C A A Z 0B = 0 Graphing an Equation in General Form Using Its Intercepts Graph the equation by finding its intercepts.2x + 4y = 8 EXAMPLE 9 Solution To obtain the x-intercept, let in the equation and solve for x. Let Divide both sides by 2.x = 4 2x = 8 y = 0.2x + 4102 = 8 2x + 4y = 8 y = 0 *Some books use the term standard form.
  • 58. SECTION 1.3 Lines 27 9 Find Equations of Parallel Lines When two lines (in the plane) do not intersect (that is, they have no points in common), they are said to be parallel. Look at Figure 43.There we have drawn two parallel lines and have constructed two right triangles by drawing sides parallel to the coordinate axes.The right triangles are similar. (Do you see why? Two angles are equal.) Because the triangles are similar, the ratios of corresponding sides are equal. THEOREM Criterion for Parallel Lines Two nonvertical lines are parallel if and only if their slopes are equal and they have different y-intercepts. The use of the words “if and only if” in the preceding theorem means that actually two statements are being made, one the converse of the other. If two nonvertical lines are parallel, then their slopes are equal and they have different y-intercepts. If two nonvertical lines have equal slopes and they have different y-intercepts, then they are parallel. Showing That Two Lines Are Parallel Show that the lines given by the following equations are parallel: L1: 2x + 3y = 6, L2: 4x + 6y = 0 EXAMPLE 10 y Rise Run Run Rise x Figure 43 Lines that are neither vertical nor horizontal have general equations of the form and Because the equation of every line can be written in general form, any equation equivalent to equation (4) is called a linear equation. B Z 0A Z 0Ax + By = C Solution To determine whether these lines have equal slopes and different y-intercepts, write each equation in slope–intercept form: Because these lines have the same slope, but different y-intercepts, the lines are parallel. See Figure 44. - 2 3 , Slope = - 2 3 ; y-intercept = 2 Slope = - 2 3 ; y-intercept = 0 y = - 2 3 x + 2 y = - 2 3 x 3y = -2x + 6 6y = -4x L1: 2x + 3y = 6 L2: 4x + 6y = 0 ᭹ y 5 5 L1 L2 Ϫ5 x Figure 44 Finding a Line That Is Parallel to a Given Line Find an equation for the line that contains the point and is parallel to the line .2x + y = 6 12, -32 EXAMPLE 11 Solution Since the two lines are to be parallel, the slope of the line that we seek equals the slope of the line . Begin by writing the equation of the line in slope–intercept form. y = -2x + 6 2x + y = 6 2x + y = 62x + y = 6
  • 59. Proof Let and denote the slopes of the two lines. There is no loss in gener- ality (that is, neither the angle nor the slopes are affected) if we situate the lines so that they meet at the origin. See Figure 47.The point is on the line having slope and the point is on the line having slope (Do you see why this must be true?) Suppose that the lines are perpendicular. Then triangle OAB is a right triangle. As a result of the Pythagorean Theorem, it follows that (5) Using the distance formula, the squares of these distances are 3d1A, B242 = 11 - 122 + 1m2 - m122 = m2 2 - 2m1m2 + m1 2 3d1O, B242 = 11 - 022 + 1m1 - 022 = 1 + m1 2 3d1O, A242 = 11 - 022 + 1m2 - 022 = 1 + m2 2 3d1O, A242 + 3d1O, B242 = 3d1A, B242 m1.B = 11, m12m2, A = 11, m22 m2m1 x y Run = 1 O Rise = m1 Rise = m2 A = (1, m2) B = (1, m1 ) Slope m2 Slope m1 1 Figure 47 In Problem 128 you are asked to prove the “if” part of the theorem; that is: If two nonvertical lines have slopes whose product is , then the lines are perpendicular. -1 28 CHAPTER 1 Graphs y 6 Ϫ5 6Ϫ6 (2, Ϫ3) 2x ϩ y ϭ 1 2x ϩ y ϭ 6 x Figure 45 y 90° x Figure 46 ᭹ 10 Find Equations of Perpendicular Lines When two lines intersect at a right angle (90°), they are said to be perpendicular. See Figure 46. The following result gives a condition, in terms of their slopes, for two lines to be perpendicular.