6 7 Circumference Arc Length Notes Circumference The

6. 7 Circumference & Arc Length Notes

Circumference The distance around a circle. Do you remember the formula? ? ? C = 2 r or C = d * Always use the button on your calculator, NOT 3. 14!!!

Ex 1: Find the circumference of a circle with a diameter of 12 cm. (Round to 2 decimal places. ) C = 2 r C = 2 (6) C = 12 cm C = 37. 70 cm * If you are asked for the exact value leave your answer in terms of . It will look like this!!! OR C = d C = (12) C = 12 C = 37. 70 cm

Ex 2: Find the radius of a circle with a circumference of 52 in. C = 2 r 52 = 2 r 8. 28 in. r

What if you only want to know the length of a piece of the circumference? ? ? This is called Arc Length It is a piece of the circumference of circle. A B

Arc Length Corollary ( The length of AB is: OR Things to keep in mind when finding arc length • The measure of an arc is in degrees. • The length of an arc is in linear units. (such as ft, cm, etc. )

( Ex 1: Find the length of JK. C 60 o J 16 in. K Put in calc!!

( Your Turn: Find the length of AB. A 150 o 34 cm. B

( Ex 2: Find the m LM. Notice that we are given the arc length and need to find the measure of the arc!! 16. 76 in. L . n i 8 M C Put in calc!!

( Your Turn: Find the m AB. 18. 84 m. B. n i 9 C A

Ex 3: Find the circumference of circle C. R 10. 2 cm 45 o S C Put in calc!!

Your Turn: Find the circumference of circle C. A 200 o C 41. 87 cm B

Your Turn: Find the radius of circle C. READ the directions carefully!!! R 45 o C 1. 57 ft S