What is the unit circle used for?

The unit circle is used to understand the sin, cos, and tan of angles in a circle. At the high school level that we are learning this at it really doesnt make too much sense. But if you are the next Einstein and want to learn more about what its used for and what its mathematical properties are we suggest going here: http://en.wikipedia.org/wiki/Unit_circle or              https://scs.imsa.edu/wiki/index.php/The_Unit_Circle