Coterminal Angles in Radians

Thus far, we have measured everything in degree mode. The second way to measure an angle is in radians, which is in reference to the circumference of a circle. Radians always have the term π as part of the expression.

To convert from degrees or radians, we must multiply by either (π/180) or by (180/π). Use the first one to convert to radians and the second one to convert to degrees.

Finally, we made the trig unit circle in both degrees and radians for our reference. You may use this reference sheet on a quiz or a test. The trig unit circle is the image shown below, and it shows commonly used angles in trigonometry.