Unit circle

circle with radius one
The Unit Circle can be used to model every Trigonometric function.

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.

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  .

 
The unit circle can substitute variables for trigonometric functions.