This document discusses using symmetry as a problem solving tool in mathematics education. It presents six mathematical problems that can be solved using different types of symmetry, such as geometric, algebraic, and role symmetry. The problems were used in workshops for secondary mathematics teachers to develop their understanding and preference for using symmetry. Initially, teachers did not often use symmetry in their own problem solving approaches. Through discussion of alternative symmetric solutions, teachers' inclination to utilize symmetry gradually increased over the course of the intervention.
255 Compiled And Solved Problems In Geometry And TrigonometryCarrie Tran
The document contains a table of contents for a book titled "255 Compiled and Solved Problems in Geometry and Trigonometry" by Florentin Smarandache. The book contains problems from Romanian textbooks on geometry and trigonometry for 9th and 10th grade, compiled and solved by the author when he was a mathematics professor in Romania and Morocco. It includes two-dimensional and three-dimensional Euclidean geometry problems as well as trigonometry, ranging from easy to difficult. The book is intended as a teaching resource for mathematics students and instructors.
Compiled and solved problems in geometry and trigonometry,F.SmaradanheΘανάσης Δρούγας
This document contains 29 geometry problems from Romanian textbooks for 9th and 10th grade students, compiled and solved by Florentin Smarandache. The problems cover a range of topics in geometry including properties of angles, triangles, polygons, circles, areas, and constructions. Smarandache compiled these problems during his time teaching mathematics in Romania and Morocco between 1981-1988. He provides solutions to each problem at the end of the document to serve as an educational aid for mathematics students and instructors.
Excel in the concepts of coordinate geometry by knowing everything from important topics, preparation tips and formulas to practical applications. Read the complete article to know more:
This document provides a curriculum map for 8th grade mathematics for the first quarter. Students will develop an understanding of irrational numbers by approximating them with rational numbers. They will use square roots and cube roots to solve equations. Students will also apply the Pythagorean theorem and its converse to solve problems involving right triangles. Additionally, they will learn to solve linear equations with rational number coefficients.
The document provides information about the revised mathematics syllabus for classes 9-10 in India. Some key points:
- The syllabus was revised in accordance with the National Curriculum Framework of 2005 and recommendations from experts to meet the needs of all students.
- At the secondary level, mathematics aims to help students apply algebraic and trigonometric concepts to solve real-life problems.
- The syllabus covers topics like number systems, algebra, geometry, trigonometry, mensuration, statistics, and coordinate geometry.
- Teaching methods should include activities using concrete materials, models, and experiments to make mathematics engaging and applicable.
This document contains lesson materials on lines and angles including:
- Solving two equations involving variables w and v
- Vocabulary terms related to lines and angles
- Identifying different angle relationships (corresponding angles, interior angles, etc.) when lines are cut by a transversal
- Worked examples of finding missing angle measures using properties of parallel lines
The purpose of this communication is to generalize the theorem of Pythagoras using the corresponding area formulas for different geometric figures used in experience; the aim is to look at the possibility of Demosthenes this relationship using different geometric figures squared, showing how calculators can be used to explore the situation and give account of the difficulties that students with geometric concepts.
1. Assume that an algorithm to solve a problem takes f(n) microse.docxSONU61709
1. Assume that an algorithm to solve a problem takes f(n) microseconds for some function f of the input size n. For each time t labeled across the top, determine the exact largest value of n which can be solved in time f(n) where f(n) ≤ t. Use a calculator! You will find it helpful to convert the t values to microseconds, and you may find it helpful to insert a row for n. Note that “lg n” is the log2 n. Note that the only row you can’t write out the values for fully is the “lg n” row—only there may you write 2x for the appropriate value of x. Use the Windows built-in scientific calculator (under Accessories menu) as necessary. A couple values are filled in to get you started. Important: “exact values” means precisely that. Check your answers with values above and below!
Time t =
f(n) =
1 second
1 hour
1 day
1 month
=30 days
n2
1,609,968
lg n
n3
2n
n lg n
2,755,147,513
2. Use loop counting to give a O( ) characterization of each of the following loops basing each upon the size of its input:
a. Algorithm Loop1(n):
s ← 0
for i ← 1 to n do
s ← s + i
b. Algorithm Loop2(p):
p ← 1
for i ← 1 to 2n do
p ← p * i
c. Algorithm Loop3(n):
p ← 1
for j ← 1 to n2 do
p ← p * i
d. Algorithm Loop4(n):
s ← 0
for j ← 1 to 2n do
for k ← 1 to j do
s ← s + j
e. Algorithm Loop5(n):
k ← 0
for r ← 1 to n2 do
for s ← 1 to r do
k ← k + r
3. Order the following functions from smallest to largest by their big-O notation—you can use the letters in your answer rather than copying each formula. Be clear which is smallest and which is largest, and which functions are asymptotically equivalent. For example, if g, h, and m are all O(n lg n), you would write g = h = m = O(n lg n).
a. 562 log3 108
b. n3
c. 2n lg n
d. lg nn
e. n3 lg n
f. (n3 lg n3)/2
g. nn
h. 56n
i. log5 (n!)
j. ncos n
k. n / lg n
l. lg* n
m.
4. a. Which of these equations is true, and why?
b. Which of these is smaller for very large n?
Trisecting the Circle: A Case for Euclidean Geometry
Author(s): Alfred S. Posamentier
Source: The Mathematics Teacher, Vol. 99, No. 6 (FEBRUARY 2006), pp. 414-418
Published by: National Council of Teachers of Mathematics
Stable URL: http://www.jstor.org/stable/27972006
Accessed: 09-02-2018 18:19 UTC
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide
range of content in a trusted digital archive. We use information technology and tools to increase productivity and
facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at
http://about.jstor.org/terms
National Council of Teachers of Mathematics is collaborating with JSTOR to digitize,
preserve and extend access to The Mathematics Teacher
This content downloaded ...
255 Compiled And Solved Problems In Geometry And TrigonometryCarrie Tran
The document contains a table of contents for a book titled "255 Compiled and Solved Problems in Geometry and Trigonometry" by Florentin Smarandache. The book contains problems from Romanian textbooks on geometry and trigonometry for 9th and 10th grade, compiled and solved by the author when he was a mathematics professor in Romania and Morocco. It includes two-dimensional and three-dimensional Euclidean geometry problems as well as trigonometry, ranging from easy to difficult. The book is intended as a teaching resource for mathematics students and instructors.
Compiled and solved problems in geometry and trigonometry,F.SmaradanheΘανάσης Δρούγας
This document contains 29 geometry problems from Romanian textbooks for 9th and 10th grade students, compiled and solved by Florentin Smarandache. The problems cover a range of topics in geometry including properties of angles, triangles, polygons, circles, areas, and constructions. Smarandache compiled these problems during his time teaching mathematics in Romania and Morocco between 1981-1988. He provides solutions to each problem at the end of the document to serve as an educational aid for mathematics students and instructors.
Excel in the concepts of coordinate geometry by knowing everything from important topics, preparation tips and formulas to practical applications. Read the complete article to know more:
This document provides a curriculum map for 8th grade mathematics for the first quarter. Students will develop an understanding of irrational numbers by approximating them with rational numbers. They will use square roots and cube roots to solve equations. Students will also apply the Pythagorean theorem and its converse to solve problems involving right triangles. Additionally, they will learn to solve linear equations with rational number coefficients.
The document provides information about the revised mathematics syllabus for classes 9-10 in India. Some key points:
- The syllabus was revised in accordance with the National Curriculum Framework of 2005 and recommendations from experts to meet the needs of all students.
- At the secondary level, mathematics aims to help students apply algebraic and trigonometric concepts to solve real-life problems.
- The syllabus covers topics like number systems, algebra, geometry, trigonometry, mensuration, statistics, and coordinate geometry.
- Teaching methods should include activities using concrete materials, models, and experiments to make mathematics engaging and applicable.
This document contains lesson materials on lines and angles including:
- Solving two equations involving variables w and v
- Vocabulary terms related to lines and angles
- Identifying different angle relationships (corresponding angles, interior angles, etc.) when lines are cut by a transversal
- Worked examples of finding missing angle measures using properties of parallel lines
The purpose of this communication is to generalize the theorem of Pythagoras using the corresponding area formulas for different geometric figures used in experience; the aim is to look at the possibility of Demosthenes this relationship using different geometric figures squared, showing how calculators can be used to explore the situation and give account of the difficulties that students with geometric concepts.
1. Assume that an algorithm to solve a problem takes f(n) microse.docxSONU61709
1. Assume that an algorithm to solve a problem takes f(n) microseconds for some function f of the input size n. For each time t labeled across the top, determine the exact largest value of n which can be solved in time f(n) where f(n) ≤ t. Use a calculator! You will find it helpful to convert the t values to microseconds, and you may find it helpful to insert a row for n. Note that “lg n” is the log2 n. Note that the only row you can’t write out the values for fully is the “lg n” row—only there may you write 2x for the appropriate value of x. Use the Windows built-in scientific calculator (under Accessories menu) as necessary. A couple values are filled in to get you started. Important: “exact values” means precisely that. Check your answers with values above and below!
Time t =
f(n) =
1 second
1 hour
1 day
1 month
=30 days
n2
1,609,968
lg n
n3
2n
n lg n
2,755,147,513
2. Use loop counting to give a O( ) characterization of each of the following loops basing each upon the size of its input:
a. Algorithm Loop1(n):
s ← 0
for i ← 1 to n do
s ← s + i
b. Algorithm Loop2(p):
p ← 1
for i ← 1 to 2n do
p ← p * i
c. Algorithm Loop3(n):
p ← 1
for j ← 1 to n2 do
p ← p * i
d. Algorithm Loop4(n):
s ← 0
for j ← 1 to 2n do
for k ← 1 to j do
s ← s + j
e. Algorithm Loop5(n):
k ← 0
for r ← 1 to n2 do
for s ← 1 to r do
k ← k + r
3. Order the following functions from smallest to largest by their big-O notation—you can use the letters in your answer rather than copying each formula. Be clear which is smallest and which is largest, and which functions are asymptotically equivalent. For example, if g, h, and m are all O(n lg n), you would write g = h = m = O(n lg n).
a. 562 log3 108
b. n3
c. 2n lg n
d. lg nn
e. n3 lg n
f. (n3 lg n3)/2
g. nn
h. 56n
i. log5 (n!)
j. ncos n
k. n / lg n
l. lg* n
m.
4. a. Which of these equations is true, and why?
b. Which of these is smaller for very large n?
Trisecting the Circle: A Case for Euclidean Geometry
Author(s): Alfred S. Posamentier
Source: The Mathematics Teacher, Vol. 99, No. 6 (FEBRUARY 2006), pp. 414-418
Published by: National Council of Teachers of Mathematics
Stable URL: http://www.jstor.org/stable/27972006
Accessed: 09-02-2018 18:19 UTC
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide
range of content in a trusted digital archive. We use information technology and tools to increase productivity and
facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at
http://about.jstor.org/terms
National Council of Teachers of Mathematics is collaborating with JSTOR to digitize,
preserve and extend access to The Mathematics Teacher
This content downloaded ...
This document provides a syllabus for mathematics courses at the secondary and higher secondary levels. Some key points:
- The syllabus builds upon concepts from previous grades in a continuous manner from classes 9 to 12.
- It is designed to be taught in approximately 180 hours to allow sufficient time for exploration and understanding of concepts.
- Areas like proofs and mathematical modeling are introduced gradually from classes 9 to 12 since they are new concepts.
- The syllabus covers topics like number systems, algebra, trigonometry, coordinate geometry, geometry, mensuration, statistics and probability.
- Specific concepts outlined for each class include polynomials, linear equations, quadratic equations, trigonometric ratios and identities.
The document is a lesson transcript for a mathematics class on right angles and circles. It discusses how if the endpoints of a diameter of a circle are joined to any other point on the circle, the angle formed is a right angle. It provides definitions, facts, and concepts to the students. The lesson involves drawing circles and diameters, forming triangles, and proving that the angles are right angles. Students are asked to apply the concept to determine if angles in other drawings are right angles.
Riccati matrix differential equation has long been known to be so difficult to solve analytically and/or numerically. In this connection, most of the recent studies are concerned with the derivation of the necessary conditions that ensure the existence of the solution. Therefore, in this paper, He’s Variational iteration method is used to derive the general form of the iterative approximate sequence of solutions and then proved the convergence of the obtained sequence of approximate solutions to the exact solution. This proof is based on using the mathematical induction to derive a general formula for the upper bound proved to be converging to zero under certain conditions.
5.1 Introduction 5.2 Ratio And Proportionality 5.3 Similar Polygons 5.4 Basic Proportionality Theorem 5.5 Angle Bisector Theorem 5.6 Similar Triangles 5.7 Properties Of Similar Triangles
The document provides lecture notes for a course on matrix algebra for engineers. It covers topics such as the definition of matrices, addition and multiplication of matrices, special matrices like the identity and zero matrices, transposes, inverses, orthogonal matrices, and systems of linear equations. The notes are intended to teach the basics of matrix algebra at a level appropriate for engineering students who have taken calculus. They include video links, examples, problems at the end of each section, and solutions to the problems in an appendix.
This document provides an overview of the course "Business Mathematics" which covers topics like linear equations, nonlinear equations, and economic applications of linear and quadratic models. The course is targeted at second year ABVM students.
Unit one discusses linear equations, their basic concepts and properties. It also covers developing linear equations using the slope-intercept form, slope-point form, and two-point form. Nonlinear equations are defined as equations with terms of degree two or higher that do not represent straight lines.
Economic applications of linear and quadratic models are also discussed. Functions and curves are defined in economics, with examples like the relationship between money earned and hours worked given as a simple linear function.
Linear equation in one variable PPT.pdfmanojindustry
This document discusses linear equations in two variables. It defines linear equations and explains that a linear equation in two variables can be written as ax + by = c, where a, b, and c are real numbers and a and b are not both equal to zero. It also explains that a linear equation in two variables has infinitely many solutions and that the graph of a linear equation is a straight line. The document provides examples of linear equations and their graphical representations.
Linear Algebra may be defined as the form of algebra in which there is a study of different kinds of solutions which are related to linear equations. In order to explain the Linear Algebra, it is important to explain that the title consists of two different terms. The very first term which is important to be considered in the same, is Linear. Linear may be defined as something which is straight. Linear equations can be used for the calculation of the equation in a xy plane where the straight lines has been defined. In addition to this, linear equations can be used to define something which is straight in a three dimensional perspective. Another view of linear equations may be defined as flatness which recognizes the set of points which can be used for giving the description related to the equations which are in a very simple forms. These are the equations which involves the addition and multiplication.
This document describes a lesson plan for teaching students about transformations of quadratics. The lesson uses TI-Inspire software to allow students to explore how changing the coefficients a, b, and c affects the graph of a quadratic function. Students will first investigate how a affects the shape of the graph using sliders. They will then explore how b changes the location of the vertex and how c changes the y-intercept. Finally, students will graph multiple functions with roots of 3 and 5 to analyze similarities and differences between the graphs. The technology enables efficient exploration and comparison of graphs to build conceptual understanding of quadratic transformations.
This document discusses conic sections, which are plane curves formed by the intersection of a cone with a plane. The four types of conic sections are circles, ellipses, parabolas, and hyperbolas. It provides examples of how to determine the equation of a conic section based on given properties, such as all points being equidistant from a fixed point and line. Key aspects covered include using the distance formula and completing the square to put equations in standard form.
This document discusses the relationships between various geometry and algebra topics and the topic of vectors, specifically addition and subtraction of vectors. Polygons, parallel lines, algebraic expressions, and straight lines are all related to vectors because vectors represent straight lines with direction and magnitude. Examples are given of using concepts like the parallelogram law, triangle law, and algebraic expressions to solve vector addition and subtraction problems.
APEX INSTITUTE has been established with sincere and positive resolve to do something rewarding for ENGG. / PRE-MEDICAL aspirants. For this the APEX INSTITUTE has been instituted to provide a relentlessly motivating and competitive atmosphere.
This document discusses the relationships between various mathematical concepts and the topic of vectors, specifically addition and subtraction of vectors. It provides examples of how polygons, parallel lines, algebraic expressions, and straight lines all relate to vectors. Polygons and parallel lines can be used to understand vector addition and subtraction through laws like the parallelogram law. Algebraic expressions allow expressing vectors in terms of other vectors. And vectors are straight lines with direction and magnitude, making straight lines a basic concept for understanding vectors.
This module introduces geometric relationships between lines and angles. It discusses parallel and perpendicular lines, and defines perpendicular bisectors of line segments. It also covers exterior angles of triangles and triangle inequalities involving side lengths and angle measures. Key concepts taught include the perpendicular bisector theorem, exterior angle theorem, triangle inequality theorem, and the Pythagorean theorem for right triangles. Students are expected to learn to identify and apply properties of parallel, perpendicular and intersecting lines, and solve problems involving triangle inequalities.
Here are some suggestions for extending the lesson:
- Have learners solve more complex problems involving multiple applications of trigonometric ratios, Pythagoras' theorem and angle properties. Real-world scenarios work well.
- Introduce the unit circle and have learners locate trig function values for angles between 0-360 degrees.
- Review trig identities like sin^2(x) + cos^2(x) = 1 and extend to derive others like 1 + tan^2(x) = sec^2(x).
- Introduce the inverse trig functions (arcsin, arccos, arctan) and have learners practice evaluating and using them.
- For advanced
The document discusses the challenges of writing an essay about one's favorite book, noting that it is difficult to balance subjective personal sentiments with objective literary analysis. It explains that an effective essay on this topic must convey passion for the book while maintaining critical evaluation, address why the book had an emotional impact without relying on cliches, and engage readers who may not initially share the same view. The document advises that transforming personal admiration for a book into a compelling narrative requires careful consideration of language, structure, and reader engagement.
185 Toefl Writing Topics And Model Essays PDF - DownlJody Sullivan
The chapter summarizes Elizabeth Pisani's book "The Wisdom of Whores" which critiques the international response to the AIDS epidemic. It discusses Pisani's frustration with the approaches taken by international organizations, governments, NGOs, and activists. While data-driven, the book was seen as controversial in how it portrayed these responses. The chapter provides an overview of Pisani's perspective that the data showed some approaches were ineffective and highlights both her critiques and hopes for progress made.
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This document provides a syllabus for mathematics courses at the secondary and higher secondary levels. Some key points:
- The syllabus builds upon concepts from previous grades in a continuous manner from classes 9 to 12.
- It is designed to be taught in approximately 180 hours to allow sufficient time for exploration and understanding of concepts.
- Areas like proofs and mathematical modeling are introduced gradually from classes 9 to 12 since they are new concepts.
- The syllabus covers topics like number systems, algebra, trigonometry, coordinate geometry, geometry, mensuration, statistics and probability.
- Specific concepts outlined for each class include polynomials, linear equations, quadratic equations, trigonometric ratios and identities.
The document is a lesson transcript for a mathematics class on right angles and circles. It discusses how if the endpoints of a diameter of a circle are joined to any other point on the circle, the angle formed is a right angle. It provides definitions, facts, and concepts to the students. The lesson involves drawing circles and diameters, forming triangles, and proving that the angles are right angles. Students are asked to apply the concept to determine if angles in other drawings are right angles.
Riccati matrix differential equation has long been known to be so difficult to solve analytically and/or numerically. In this connection, most of the recent studies are concerned with the derivation of the necessary conditions that ensure the existence of the solution. Therefore, in this paper, He’s Variational iteration method is used to derive the general form of the iterative approximate sequence of solutions and then proved the convergence of the obtained sequence of approximate solutions to the exact solution. This proof is based on using the mathematical induction to derive a general formula for the upper bound proved to be converging to zero under certain conditions.
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The document provides lecture notes for a course on matrix algebra for engineers. It covers topics such as the definition of matrices, addition and multiplication of matrices, special matrices like the identity and zero matrices, transposes, inverses, orthogonal matrices, and systems of linear equations. The notes are intended to teach the basics of matrix algebra at a level appropriate for engineering students who have taken calculus. They include video links, examples, problems at the end of each section, and solutions to the problems in an appendix.
This document provides an overview of the course "Business Mathematics" which covers topics like linear equations, nonlinear equations, and economic applications of linear and quadratic models. The course is targeted at second year ABVM students.
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Economic applications of linear and quadratic models are also discussed. Functions and curves are defined in economics, with examples like the relationship between money earned and hours worked given as a simple linear function.
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This document discusses linear equations in two variables. It defines linear equations and explains that a linear equation in two variables can be written as ax + by = c, where a, b, and c are real numbers and a and b are not both equal to zero. It also explains that a linear equation in two variables has infinitely many solutions and that the graph of a linear equation is a straight line. The document provides examples of linear equations and their graphical representations.
Linear Algebra may be defined as the form of algebra in which there is a study of different kinds of solutions which are related to linear equations. In order to explain the Linear Algebra, it is important to explain that the title consists of two different terms. The very first term which is important to be considered in the same, is Linear. Linear may be defined as something which is straight. Linear equations can be used for the calculation of the equation in a xy plane where the straight lines has been defined. In addition to this, linear equations can be used to define something which is straight in a three dimensional perspective. Another view of linear equations may be defined as flatness which recognizes the set of points which can be used for giving the description related to the equations which are in a very simple forms. These are the equations which involves the addition and multiplication.
This document describes a lesson plan for teaching students about transformations of quadratics. The lesson uses TI-Inspire software to allow students to explore how changing the coefficients a, b, and c affects the graph of a quadratic function. Students will first investigate how a affects the shape of the graph using sliders. They will then explore how b changes the location of the vertex and how c changes the y-intercept. Finally, students will graph multiple functions with roots of 3 and 5 to analyze similarities and differences between the graphs. The technology enables efficient exploration and comparison of graphs to build conceptual understanding of quadratic transformations.
This document discusses conic sections, which are plane curves formed by the intersection of a cone with a plane. The four types of conic sections are circles, ellipses, parabolas, and hyperbolas. It provides examples of how to determine the equation of a conic section based on given properties, such as all points being equidistant from a fixed point and line. Key aspects covered include using the distance formula and completing the square to put equations in standard form.
This document discusses the relationships between various geometry and algebra topics and the topic of vectors, specifically addition and subtraction of vectors. Polygons, parallel lines, algebraic expressions, and straight lines are all related to vectors because vectors represent straight lines with direction and magnitude. Examples are given of using concepts like the parallelogram law, triangle law, and algebraic expressions to solve vector addition and subtraction problems.
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This module introduces geometric relationships between lines and angles. It discusses parallel and perpendicular lines, and defines perpendicular bisectors of line segments. It also covers exterior angles of triangles and triangle inequalities involving side lengths and angle measures. Key concepts taught include the perpendicular bisector theorem, exterior angle theorem, triangle inequality theorem, and the Pythagorean theorem for right triangles. Students are expected to learn to identify and apply properties of parallel, perpendicular and intersecting lines, and solve problems involving triangle inequalities.
Here are some suggestions for extending the lesson:
- Have learners solve more complex problems involving multiple applications of trigonometric ratios, Pythagoras' theorem and angle properties. Real-world scenarios work well.
- Introduce the unit circle and have learners locate trig function values for angles between 0-360 degrees.
- Review trig identities like sin^2(x) + cos^2(x) = 1 and extend to derive others like 1 + tan^2(x) = sec^2(x).
- Introduce the inverse trig functions (arcsin, arccos, arctan) and have learners practice evaluating and using them.
- For advanced
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1. Applications of symmetry to problem solving
ROZA LEIKIN,*{ ABRAHAM BERMAN{ and ORIT ZASLAVSKY{
{ Faculty of Education, University of Haifa, Haifa, 31905, Israel
{ Technion, Israel Institute of Technology, Haifa, 32000, Israel; e-mail:
rozal@construct.haifa.ac.il
(Received 4 January 1999)
Symmetry is an important mathematical concept which plays an extremely
important role as a problem-solving technique. Nevertheless, symmetry is
rarely used in secondary school in solving mathematical problems. Several
investigations demonstrate that secondary school mathematics teachers are not
aware enough of the importance of this elegant problem-solving tool. In this
paper we present examples of problems from several branches of mathematics
that can be solved using diVerent types of symmetry. Teachers’ attitudes and
beliefs regarding the use of symmetry in the solutions of these problems are
discussed.
1. Introduction
Research on mathematical problem solving emphasizes the potential of
problem solving in: (a) developing students’ mathematical ability, their intuitions
and reasoning; (b) enhancing students’ motivation and enthusiasm with respect to
mathematics [1–6]. The concept of symmetry has a special role in problem solving.
The importance of the role of symmetry in problem solving is expressed by Polya
[7] as follows:
We expect that any symmetry found in the data and conditions of the
problem will be mirrored by the solution ([7], p. 161)
Symmetry connects between various branches of mathematics such as algebra,
geometry, probability, and calculus [8–19]. Nevertheless, symmetry is rarely used
in secondary school mathematics as a problem-solving technique.
Teachers’ perceptions of a particular mathematical concept and their beliefs
about its role in problem solving strongly inuence the kinds of learning
experiences they design for their students, and consequently the processes of
learning mathematics in their classrooms. Dreyfus and Eisenberg [20] claim that
teachers need to develop awareness of the importance of symmetry for secondary
school mathematical problem solving. They support this claim by their Žnding
that high school mathematics teachers who participated in an investigation
conducted by Dreyfus and Eisenberg [20] did not recognize symmetry as a tool
that can simplify the solutions.
This paper is based on a study, which focused on symmetry as a tool for
professional development of mathematics teachers [11]. In the framework of this
int. j. math. educ. sci. technol., 2000, vol. 31, no. 6, 799–809
International Journal of Mathematical Education in Science and Technology
ISSN 0020–739X print/ISSN 1464–5211 online # 2000 Taylor & Francis Ltd
http://www.tandf.co.uk/journals
* Author for correspondence.
2. study a careful analysis of the Israeli secondary mathematics curriculum has been
made in order to identify problems related to diVerent mathematical topics that
could be solved using symmetry. The problems were applied in a series of
workshops for mathematics teachers on the use of symmetry in problem solving.
In order to follow their preferences and tendencies regarding the use of symmetry,
the workshops were designed to document processes in which the teachers were
involved.
Symmetry was deŽned in the study as follows:
DeŽnition. Symmetry is a triplet consisting of an object …S†, a speciŽc property
…Y† of the object, and a transformation …M† satisfying the following two conditions:
(i) The object belongs to the domain of the transformation.
(ii) Application of the transformation to the object does not change the
property of the object.
Symmetry …S; Y; M† is called a trivial symmetry if property Y is immune to
transformation M for any object S having this property.
This deŽnition covers diVerent types of symmetry such as geometric symmetry
(see, for example, Problems 1 and 2 for line symmetry, Problem 3 for central
symmetry and Problem 4 for rotational symmetry), algebraic role symmetry (see,
for example, Problems 5 and 6), and role symmetry in proofs (see, for example,
Problem 2).
The purpose of this paper is to present symmetry as a powerful problem-
solving tool in secondary mathematical curriculum, and to discuss teachers’
attitudes and preferences towards this tool. In section 2 we present examples of
mathematical problems, which can be solved using symmetry. These problems
were introduced to teachers in diVerent ways, which are described in section 3.
We conclude in section 4 with a discussion of the inuence of this intervention on
teachers’ attitudes and beliefs regarding application of symmetry.
2. Examples
In this section we present six problems and demonstrate how to solve them
using symmetry. Problem 1 is a classical example of a question that can be solved
using symmetry. Problems 2 and 5 are taken from Arbel [21] and Polya [7],
respectively, in which they are solved using symmetry. Problems 3, 4 and 6 are
taken from Israeli textbooks and tests in chapters that do not make any connections
to the concept of symmetry.
Problems 1 and 2 are optimization problems that usually are associated with
use of calculus. The solutions presented below are based on geometric symmetry,
i.e. line symmetry.
Problem 1. Given a point P in an acute angle. Find points A and B on the
angle’s sides, such that perimeter of the triangle ABP is minimal (Žgure 1).
Solution. Let P0
and P00
be two points that are symmetrical to P with respect
to the sides m and n respectively. Then point A on m and point B on n fulŽl the
conditions AP0
ˆ AP and BP00
ˆ BP and the perimeter of the triangle ABP
…PA ‡ AB ‡ BP† is equal to the sum of segments P0
A ‡ AB ‡ BP00
(Žgure 2).
800 R. Leikin et al.
3. Let A¤
and B¤
be the intersection points of the segment P0
P00
with lines m and n
respectively, then for every A on m and B on m such that A and B are diVerent
from A¤
and B¤
, P0
A¤
‡ A¤
B¤
‡ B¤
P00
< P0
A ‡ AB ‡ BP00
. Thus, the triangle
A¤
B¤
P has minimal perimeter.
In the following problem we use role symmetry in proof in addition to geometric
symmetry.
Problem 2. Given an acute angled triangle ABC. Find a triangle PQR
inscribed in the triangle ABC having minimal perimeter (Žgure 3).
Solution. Let P1 be a point in the side BC of the given triangle and points P0
1
and P00
1 symmetrical to P1 with respect to the lines AB and AC. According to
Problem 2, for this particular point P1 the triangle P1Q1R1 is of the minimal
perimeter if Q1 and R1 are the intersection points of the segment P0
1P00
1 with sides
Applications of symmetry 801
Figure 1.
Figure 2.
4. AB and AC of the triangle (Žgure 4). The perimeter of the triangle P1Q1R1 is equal
to the length of the segment P0
1P00
1 .
For any point Pi in BC the triangle P0
i AP 00
i is an isosceles triangle (AP0
i ˆ
APi ˆ AP00
i as symmetrical segments). For any i, the angle P0
i AP 00
i ˆ 2BAC and
therefore constant (Žgure 5). Of all the isosceles triangles with equal angles
opposite to the bases, the triangle having the shortest lateral side has the shortest
base. Hence, P0
i P00
i is minimal when APi is minimal, in other words, when APi is an
altitude of the triangle ABC.
The perimeter of the triangle PiQiRi is equal to the length of the segment P0
i P00
i
and its length is minimal when APi is minimal. Hence P¤
Q¤
R¤
is of the minimal
perimeter if and only if P¤
A is the altitude of the triangle (Žgure 6).
The points P, Q and R play symmetrical roles in the problem. Thus all three
points P¤
, Q¤
, and R¤
are heels of altitudes of the given triangle (Žgure 7). Hence,
802 R. Leikin et al.
Figure 3.
Figure 4.
5. of all the triangles inscribed in the acute angled triangle ABC the triangle with
vertices in the heels of the altitudes of the given triangle has minimal perimeter.
The solution to Problem 3 is based on central symmetry instead of rather
complicated calculus manipulations.
Problem 3. Given the quadratic function y ˆ x2
¡ 3 and a family of linear
functions y ˆ ax ‡ 3, for which value of the parameter a is the area of the region
bounded by the parabola and by the line minimal (Žgure 8)?
Solution. Consider the line y ˆ 3. The Žgure bounded by the parabola and by
this line is symmetrical with respect to the y-axis. Each line …`: y ˆ ax ‡ 3†
diVerent from y ˆ 3 ‘breaks’ the symmetry of this Žgure (Žgure 9).
Applications of symmetry 803
Figure 5.
Figure 6.
6. Let the line y ˆ 3 intersect the parabola at points P and M. Let line ` intersect
the parabola at the points L and S and the y-axis at Q. Let PN and MK be parallel
to the y axis where points N and K are on ` . Triangles QPN and QMK are
symmetrical with respect to the point Q, then SLMQ > SKMQ ˆ SNPQ > SSPQ.
Hence the region bounded by the parabola y ˆ x2
¡ 3 and by a line from the family
of functions y ˆ ax ‡ 3 is minimal when a ˆ 0.
In Problem 4 we use geometric rotational symmetry in the theory of complex
numbers.
Problem 4. Prove that the sum of all complex roots of the equation zn
ˆ 1 is
equal to 0 for all natural numbers n.
804 R. Leikin et al.
Figure 7.
Figure 8.
7. Solution. All the roots are points on the unit circle (Žgure 10).
The rotation of the circle does not change the location of the set of points.
Hence the sum of the solution vectors for z does not change. Hence this sum is
zero.
Solution of the system of equation in Problem 5 presents use of algebraic
symmetry of role.
Problem 5. Solve the following system of equations:
3x ‡ 2y ‡ z ˆ 30
x ‡ 3y ‡ 2y ˆ 30
2x ‡ y ‡ 3z ˆ 30
8
>
<
>
:
Solution. The given system consists of three equations with three unknowns
and is invariant under cyclic permutation of the unknowns. Thus, if a triplet
…t1; t2; t3† is a solution of the system, then the triplets …t2; t3; t1† and …t3; t1; t2† are
Applications of symmetry 805
Figure 9.
Figure 10.
8. also solutions of this system. It is easy to check that the system has only one
solution, hence t1 ˆ t2 ˆ t3. Consequently: x ˆ y ˆ z, 6x ˆ 30, x ˆ y ˆ z ˆ 5.
Note. The uniqueness of the solution does not follow from symmetry.
Finally in the solution of the following problem we use both algebraic symmetry
and geometric symmetry.
Problem 6. Prove that the straight line y ˆ x intersects the ellipse
x2
‡ xy ‡ y2
ˆ 12 at right angles.
Solution. The equation of the ellipse is algebraically symmetrical. In other
words, permutation of the variables x and y does not change the equation. Hence,
if a point …a; b† belongs to the curve, then the point …b; a† also belongs to the curve.
Therefore, the curve is symmetrical with respect to line y ˆ x. The set of tangent
lines to the curve is also symmetrical with respect to the line y ˆ x. Thus, the
tangent line to the curve at the point of intersection of the curve with the line y ˆ x
is symmetrical with respect to this line, if it exists. An ellipse is convex and has a
tangent line at each of its points, therefore the tangent line to the curve at the point
of intersection of the curve with the line y ˆ x is perpendicular to this line.
3. The intervention
The problems presented above are examples of mathematical problems that
were used in a secondary mathematics teachers’ professional development pro-
gramme in order to identify their problem-solving strategies and their preferences
with respect to the use of symmetry. The teachers’ responses to the problems they
solved were recorded and analysed. The problems were presented to the teachers
in diVerent ways. For example, for Problems 1, 2, 4 and 5 the teachers were asked
to suggest as many solutions as possible before any discussion of solutions took
place. On the other hand, for Problem 6, two diVerent solutions were presented to
the teachers by the researcher, one of which was based on symmetry and the other
was based on more conventional ways typically used in secondary school. Follow-
ing the presentation of the two diVerent solutions, the teachers were asked to
choose one of these suggested ways when solving a similar problem. Succeeding
their engagement with the problems, teachers were involved in authentic discus-
sions focused on advantages and disadvantages of the diVerent kinds of solutions.
Additionally, the teachers were asked about their own preferences regarding the
use of symmetry in problem solving. Problem 3 was brought by a group of teachers
who knew how to solve the problem using calculus but, having gained appreciation
of symmetry, asked us to help them to use symmetry in solving the problem.
4. Discussion
In this section we discuss the main factors that inuenced teachers’ problem-
solving performance and their preferences to use symmetry in problem solving.
Our investigation demonstrated that mathematics teachers usually did not use
symmetry in problem solving. The teachers’ tendencies to use symmetry depended
on their familiarity with symmetry and on their beliefs about mathematics. As a
result of the intervention, teachers’ inclinations to use symmetry in solving
mathematical problems were enhanced. For example, at the beginning of the
806 R. Leikin et al.
9. study teachers tended not to use role symmetry at all, later on they began to ‘feel
symmetry’, and by the end of the intervention they used symmetry in solving most
of the problems.
As noted above, at the beginning of the study few teachers used symmetry
when solving the problems. Moreover, when these teachers presented their
solutions based on symmetry, they were not able to convince the other teachers
that the use of symmetry in their solution was suYcient.
For example, when Problem 1 was solved using geometric symmetry the
teachers tended to try to ‘complete’ a solution by conventional tools such as
derivative and congruency. One of the teachers claimed that ‘we need to use both
symmetry and congruence of segments in order to prove that these segments are
equal’.
Role symmetry in proofs was the most diYcult type of symmetry for teachers
to accept. When the teachers were asked to explain why the vertices Q¤
, and R¤
of
the inscribed triangle are ‘heels’ of the altitudes of the given triangle (see solution
to Problem 2 above) several teachers justiŽed it by using similarity and congru-
ence. These teachers seemed to reject the use of role symmetry. Other teachers
only partly accepted the idea of role symmetry. For these teachers it was ‘clear’
that:
If the construction started in the side BC, the ‘heel’ of the altitude to the side
BC …P¤
† was obtained as a vertex of the inscribed triangle P¤
Q¤
R¤
having the
minimal perimeter. Then, in the same way, the heels of altitudes to the sides
AC and AB of the given triangle (points Q¤¤
and R¤ 0
) could be obtained as
vertices of two other triangles: Q¤¤
R¤¤
P¤¤
and R¤ 0
P¤ 0
Q¤ 0
. Thus, the peri-
meters of these triangles must be compared and the smallest one has to be
chosen.
Only one teacher could explain how ‘thinking symmetry’ helped in proving the
statement. He solved the problem as follows:
For any point P in BC which diVers from P¤
the perimeter of the inscribed
triangle with vertex P is greater than the perimeter of the obtained triangle
P¤
Q¤
R¤
. The same consideration holds with respect to any point Q which
diVers from Q¤
and to any point R which diVers from R¤
. Hence, these three
points are ‘heels’ of the altitudes of the given triangle.
As mentioned above, teachers’ beliefs about the nature of mathematical proof as
well as their familiarity with symmetry inuenced their preferences regarding use
of symmetry in problem solving. For example, when the teachers were presented
with two diVerent solutions to Problem 6 all of them agreed that the solution based
on symmetry was more elegant and beautiful. Nevertheless, most of the teachers
thought that the solution using calculus was more ‘trustworthy’. They felt more
‘safe’ to teach their students to solve problems using calculus. In addition, when
the teachers were asked to choose one of the presented solutions of Problem 6 in
order to solve a similar problem, only two teachers chose to use symmetry in their
solutions but were not sure that the solution based on symmetry was ‘good
enough’. In order to be on the ‘safe’ side, these teachers also solved the problem
in a standard way. During the discussion of the problem one of the teachers said
that the presented solution is ‘too sophisticated and philosophical’.
Applications of symmetry 807
10. It is interesting to note that while the intervention enhanced the teachers’
knowledge of symmetry it did not equally inuence their beliefs regarding what
constitutes a valid mathematical proof. Although, at the end of the study most of
the teachers were able to use diVerent types of symmetry in problem solving, and
even solved problems using symmetry, still, many were not convinced that the
proofs were ‘mathematical enough’. For example one of the teachers, who solved
the problem using role symmetry, presented this solution to the other teacher and
then concluded: ‘but this is not mathematics, this is . . . ’. Only by the end of the
intervention were most of the teachers able and willing to use symmetry in
problem solving. Teachers’ perception of the solutions based on symmetry as
‘more elegant’ and conveying the beauty of mathematics served as a springboard
for these changes. Almost 50% of the teachers who preferred not to use symmetry
at the beginning of the study were convinced by their experience in our investiga-
tion that it is worthwhile. At the end of our study most of the teachers decided to
solve Problem 8 using symmetry. All the teachers agreed that this solution was
easier, more interesting, and more elegant.
The way in which Problem 3 was raised by the teachers themselves, is also an
indication of changes in teachers’ tendencies to use symmetry when solving the
problems. The teachers solved this problem with their twelfth-grade students
using calculus. In their opinion this solution was too complicated and they felt that
‘this problem can be solved with the help of symmetry’. When in our workshop the
teachers solved this problem using symmetry they enjoyed the fact that they
‘found such a good example for the use of symmetry’. Moreover, as a result of our
investigation the teachers seemed to be convinced that:
‘Special cases of symmetric objects are often prime candidates for ex-
amination’
([5], p. 81)
Acknowledgements
The study was supported by the Technion Project for the Enhancement of
Secondary Mathematics Education directed by O. Zaslavsky. The work of A.
Berman was supported by the Fund for the Promotion of Research at the
Technion. The Žrst draft of this paper was prepared while the Žrst author was a
post-doctoral fellow with Ed Silver at the Learning Research and Development
Center, University of Pittsburgh.
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Applications of symmetry 809