1. Section 11.4 Circumference and Arc Length
CAS 8, 19, 21
Section 11.4 Circumference and Arc Length
Goal 1: Finding Circumference and Arc Length
Goal 2: Circumference

2. Circumference
The circumference of a circle is the distance around the circle.
The ratio of the circumference to the diameter is the same for ALL circles. That ratio is pi
Circumference

3. Theorem 11.6 Circumference of a Circle
“d” is the diameter
“r” is the radius

4. Ex 1 Circumference
Find the circumference of a circle with diameter 11in

5. Arc Length
An Arc Length is a portion of the circumference of a circle. They use linear units like feet, inches, meters, etc. not degrees (like in the measure of the arc) IMPORTANT: The length of an arc is NOT the same as the measure of an arc.

6. Arc Length Corollary Arc Length of AB Portion of 360° 360°
Portion of Circumference
Circumference = A B

7. Ex. 2 Find the missing Arc length or Arc Measure
Find mTUV if the arc length of TUV is 27ft. U T S
6.3ft V

8. Ex. 3 Find the circumference

9. Ex. 4 Find the circumference of a circle whose equation is:

10. Semicircles and Qtr Circles
The length of a semicircle is one half the circumference, and the length of a 90 degree arc is one quarter of the circumference.
semicircle
Quarter of a circle

11. Ex. 5 Find the perimeter of the enclosed region.