Sine and Cosine Functions

The sine and cosine functions are ratios of the sides of a right triangle. To understand these ratios, we must first make three definitions.

First, the hypotenuse is always the longest side, H.

If an angle is defined with respect to one of the sides, then this side is called the adjacent side, A.The side opposite this angle is called the opposite side, O.

RightTriangle.gif (2239 bytes)

Here are the definitions of the sine and cosine of a given angle q:

SIN(q) = O/H, COS(q) = A/H.

Furthermore, we can define the tangent of the angle q as TAN(q) = O/A.