Base Functions for Sine and Cosine

Not only can we use sine and cosine to find missing sides of a right triangle, or points on the unit circle, but we can also graph them as functions of x and y on the coordinate plane. We graph them using degrees found on the unit circle. Sine's base function is y = sinx, and cosine's base function is y = cosx, and they look like this:

Both sine and cosine have infinite domains from negative infinity to positive infinity. Both of their ranges are from -1 to 1. And both repeat themselves after 360 degrees. When a function repeats, we call it a periodic function. Both of the periods of sine and cosine are from 0 - 360. The only difference between sine and cosine are that sine begins and ends at 0, while cosine begins and ends at 1.