Warm-UpFind the following.

1.) sin 30◦

2.) cos 270 ◦

3.) cos 135 ◦

13.3 Radian Measure

Central Angle – An angle with a vertex at the center of a circle.

Intercepted Arc – Portion of the circle with endpoints on the sides of the central angle and remaining points within the interior of the angle.

Radian – Another way to measure angles.

a radian is a central angle that intercepts an arc that is the same length as the radius of the circle

How many radians are there in a circle? How can we find this?

Converting Between Radians and DegreesTo convert degrees to radians, multiply by

To convert radians to degrees, multiply by

180

radians

radians

180

Examples: Convert degrees measure to radians.

1.) 45◦ 2.) 225◦ 3.) 150◦

Convert from radians to degrees.

 4.) Radians 5.) Radians 6.) 2 Radians

4

3

3

Ex 7: Find the exact values of cos and sin of radians. 4