10.2 circles 1

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10.2 circles 1

  1. 1. Lesson 10.1, For use with pages 521-526Find the area of the triangle and rectangle. 1. 2. 3 ft 15 m 4 ft 15 m
  2. 2. Lesson 10.1, For use with pages 521-526Find the area of the triangle and rectangle. 1. 2. 3 ft 15 m 4 ft 15 mANSWER 6 ft2 ANSWER 225 m2
  3. 3. Bell WorkTalk with your partner about the homeworkthat is due today. If it is a book assignment, please open your book so you can look back at the question.Discuss each of the following questions witheach problem from homework: How did you solve the problem? Why did you solve it that way? What did you get for your answer?
  4. 4. Circles 10.2How would you define a circle? How do you know where the center of a circle is located?
  5. 5. The distance across the center of a circle iscalled the diameter. (Line segment AB below)The distance from the center to the edge of acircle is called the radius. (Segment CD)TWO RADII = One Diameter or the radius is ½ diameter A D D÷2=R C g B
  6. 6. The distance around a circle is called thecircumference.C = π d or C = π 2 r
  7. 7. C = π d or C = π 2 rFind the circumference: (round to nearest tenth) r = 4 in C=π2r C = 3.14 x 2 x 4 C= 25.1 in
  8. 8. C = π d or C = π 2 rFind the circumference:(round to nearest tenth) d = 7 cm C=πd C = 3.14 x 7 C= 22.0 cm
  9. 9. Area of a circle is still the number ofSQUARE UNITS inside the closed figure.The area formula is A = π r2 read Pi times the radius squared and itmeans Pi x radius x radius
  10. 10. A = π r2Find the area of the circle below A = π r2D = 10 in A = 3.14 x 52 A=78.5 in sq
  11. 11. A = π r2Find the area of the circle below A = π r2r = 3 cm A = 3.14 x 32 A= 28.3 in sq
  12. 12. GUIDED PRACTICE for Examples 1 and 2Find the area and circumference of the circle.Use 3.14 for л. 1. r = 7 ft SOLUTION A = лr 2 C = 2лr = 3.14 (7)2 = 2x 3.14 x 7 = 153.9 ft2. = 44.0 ft
  13. 13. GUIDED PRACTICE for Examples 1 and 2Find the area and circumference of the circle.Use 3.14 for л. 2. d = 44 m SOLUTION A = лr 2 C = лd = 3.14 (22)2 = 3.14 x 44 = 1519.8 m2. = 138.2 m
  14. 14. HomeworkPage 529 #4-7 Find both circumference and area for each problem. ROUND TO THE NEAREST TENTH SHOW YOUR WORK!

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