Unit 1 - Objective 3 - Radians
Quick Review

The two most common measurements of angles are degrees and radians. Remember from Technical Mathematics 1 that a degree is 1/360 of a circle, and a radian is 1/2pi of a circle. An entire circle contains 360° or 2 pi radians.

To convert from degrees to radians, multiply the number of degrees by
pi/180 (approximately 0.01745) rad/degree

To convert from radians to degrees, multiply the number of radians by
180/pi (approximately 57.296) degrees/radian

Example 1

Convert 72° to radians

Example 2

Convert 3pi/4 radians to degrees

We can evaluate trigonometric functions which are in degrees or radians. If you are using a calculator, remember to have it in the proper mode.




3) cos theta = -0.9135
(You are trying to find what theta is)
theta = -142.5° or 217.5°

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