# Week 3 – Math 10 – Finding Side Lengths Using Trig

What is trigonometry (trig)?

Trigonometry is the study of triangles and the relationship of angles and sides in a triangle. Before even finding side lengths using trig, you need to label all the sides of the triangle. There are three special names for each side; there is hypotenuse, opposite, and the adjacent. The hypotenuse is the longest side and is always across from the right angle (90-degree angle). The opposite side is across from the reference angle. And the adjacent is the side beside the reference angle. What are the ratios?

SINE RATIO = opposite (divide by) hypotenuse

COSINE RATIO = adjacent (divide by) hypotenuse

TANGENT RATIO = opposite (divide by) adjacent

An easy way to memorize these ratios is with the acronym SOH CAH TOA. Therefore is each of the ratios first letters into a big word.

For every trig equation : Ratio (REFERENCE ANGLE) = side 1/side 2

In this example, we need to see what ratio we will use, and from the process of elimination the ratio needed is SINE. Next, we use algebra to find the answer. 