Unit circle
circle with radius one
In mathematics, a unit circle is a circle with a radius of 1. The equation of the unit circle is . The unit circle is centered at the Origin, or coordinates (0,0). It is often used in Trigonometry.

The Unit Circle can be used to model every Trigonometric function.
Trigonometric functions in the unit circleEdit
In a unit circle, where is the angle desired, and can be defined as and . Using the function of the unit circle, , another equation for the unit circle is found, . When working with trigonometric functions, it is mainly useful to use angles with measures between 0 and radians, or 0 through 90 degrees. It is possible to have higher angles than that, however. Using the unit circle, two identities can be found: and for any integer .