1. 11.4 Circumference and Arc Length
Arc of a Circle

2. Definitions
Circumference-The enclosing boundary of a curved geometric figure, esp. a circle.
Arc length- A fraction of the circumference

3. Theorem
The equation of the circumference

4. Find the Circumference
Radius 7

5. Find the Circumference
Radius 7

6. Find the Arc Length (often called S)
Find the Central angle θ
(the angle whose vertex is at the center),
Then multiply the Circumference by the fraction Central angle
360°

7. Find the Arc Length
Given a Central angle of 60° and a Radius of 12.

8. Find the Arc Length
Given a Central angle of 60° and a Radius of 12.

9. Find the Central angle Let R = 8 inches Length of S = 16.76 inches
Use 3.14 for pi

10. Find the Central angle Let R = 8 inches
Length of S = inches. Use 3.14 for pi

11. Find the Central angle Let R = 8 inches
Length of S = inches. Use 3.14 for pi

12. Find the Circumference
Central Angle 45°
Arc Length 10.2

13. Find the Circumference
Central Angle 45°
Arc Length 10.2

14. Homework
Page 686 – 687
# 15 – 38, 40
45, 47