Unit Circle and Sample Angles

The unit circle is a circle with radius 1 and is used to evaluate trigonometric functions.

The unit circle can tell us the measure of any angle from the origin to an (x,y) coordinate, however, angles can be more than 360 degrees on the circle, as we see in the example.



Thus at point (0,1) we have both

90 degrees or (Pi/2)
and
450 degrees or (5pi/2)

at point
(0,-1) we have 270 degrees or (3Pi/2)

Thus we see how the unit circle is used to measure angles, we will see in future posts how it relates to the trigonometric functions.