Unit Circle, Radians, and Degrees
Move the angle measure slider between 0 and 360 degrees. This will adjust the angle within unit circle. Notice that the radian measures for several angles are labeled around the circle.
The point that moves around the circle according to the angle measurement has 2 really special properties.
1) It's x and y values are given the same as the horizontal and vertical legs of the right triangle shown with green and red sides.
2) These lengths, and the x and y values of the point are EXACTLY cosine and sine of the angle. Notice that the lengths of the legs labeled are exactly the same as the cosine and sine values calculated on the right.