In a right triangle, there are three sides, these sides are based upon which angle you reference yourself from. Two sides are variable, one is not.

No matter where you reference yourself the hypoteneuse(deonted h) is always the same, but the opposite(denoted o) and the adjacent(denoted a) sides change depending from which angle you are working off of.

These three functions you speak of are geometrically defined as the

__RATIO__ between the sides of a right triangle. So for example

This means that the cosine of the angle you are at is the decimal representation of the ratio between the hypoteneuse and the side opposite of your angle..