1. 6.7 Circumference & Arc Length p.224

2. Circumference Defn. – the distance around a circle. Thm. 6.19 – Circumference of a Circle – C = 2r or C = d * Always use the  button on your calculator, NOT 3.14!!!

3. Ex: Find the circumference of a circle with a diameter of 12 cm. (Round to 2 decimal places.) C = d C = (12) C = 12 C = 37.70 cm cm C = 2r C = 2(6) C = 12 C = 37.70 cm * If asked to leave your answer in terms of , the result would look like this. OR

4. Ex: Find the radius of a circle with a circumference of 52 in. C = 2r 52 = 2r 52/2 = r 8.28 in.  r C = d 52 = d 52/ = d 16.55 in.  d So, r  16.55/2 r  8.28 in. OR

5. Arc Length Defn. – a portion of the circumference of a circle. The measure of an arc is in degrees. The length of an arc is in linear units. (such as ft, cm, etc.)

6. Arc Length Corollary The length of AB is: ( (

7. Ex: Find the length of JK. ( C J K 60 o 16 in. (

8. Arc Length Corollary Observations The length of a semicircle is ½ the circumference. The length of a 90o arc is ¼ the circumference. 180o 90 o

9. Ex: Find the m LM. ( C L M 16.76 in. 8 i n. ( ( ( ( ( (

10. Ex: Find the circumference of circle C. 45 o 10.2 cm R S C ( (

11. With a Partner, do # 1-9 pg 224 - 225