### Home > CCG > Chapter 10 > Lesson 10.1.5 > Problem 10-55

10-55.

Use the sectors in circles

What is the ratio of the arc length to the radius of circle

? Leave your answer in terms of .The arc length is

. What is the ratio of the arc length to the radius of circle

? You can use the same method as in part (a).

As in part (a), the ratio is

. The ratio of the arc length to the radius of a circle is called a

**radian**. Why will all sectors with a central angle ofhave the same radian measure? Answers may vary. Example: The circles are similar.