1. Lesson 10-7 Pages 533-538 Circumference and Area: Circles

2. What you will learn! 1. How to find the circumference of circles. 2. How to find area of circles.

3. CircleDiameter Center Circumference Radius  (pi)

4. What you really need to know! A circle is the set of all points in a plane that are the same distance from a given point.

5. What you really need to know! The ratio of the circumference of a circle to its diameter is always equal to 3.1415926... The Greek letter  (pi) stands for this number. Using this ratio, you can derive a formula for the circumference of a circle.

6. What you really need to know!

7. The area A of a circle equals the product of pi (  ) and the square of its radius r. A =  r 2 Radius

9. r ½ of the circumference ½ of 2  r

12. Example 1: Find the circumference of the circle to the nearest tenth. C =  d C =  x 12 C = 37.7 in

13. Example 2: Find the circumference of the circle to the nearest tenth. C =  d C =  x 14.2 C = 44.6 m

14. Example 3: A landscaper has a tree whose roots form a ball- shaped bulb with a circumference of about 110 inches. How wide will the landscaper have to dig a hole in order to plant the tree?

15. Example 3: C =  d 110 =  d 35.01408748 = d At least 35 inches!

16. Example 4: Find the area of the circle to the nearest tenth. A =  r 2 A =  x 11 2 A = 380.1 ft 2

17. Example 4: Find the area of the circle to the nearest tenth. A =  r 2 A =  x 4.15 2 A = 54.1 cm 2

18. Page 535-536 Guided Practice #’s 4-9

20. Pages 533-535 with someone at home and study examples! Read:

21. Homework: Pages 536-538 #’s 10-30 even #’s 37, 38, 48-53 Practice Quiz 2 #’s 1-5 Lesson Check 10-7

25. Page 749 Lesson 10-7