Introduction to the Unit Circle

A unit circle is a circle that has a radius of exactly one unit. It is a very important tool in trigonometry as it related to the trigonometric functions you learned about in the previous section. In this section we will focus on the major angles of the unit circle, in both degrees and radians. Though you can always convert between degrees and radians, please become very familiar with these angles and their conversions between degrees and radians.

The following is an example of the unit circle.

You are familiar with the angles 0° or  radians, 90° or radians, 180° or π radians, and 270° or  radians. This unit circle is further subdivided into smaller angles. Take some time to study these angles and become familiar with them so you can convert between degrees and radians easily.

Next: Section B, page 8

© 2009 KC Distance Learning. All rights reserved.