# Trigonometry

In a right angled triangle, the side opposite the right angle is called the hypotenuse.

If one of the other angles is , then we can label the remaining sides as shown in this diagram.

There are 3 trig ratios you need to know:

• sine
• cosine
• tangent

We shorten these to:

• sin
• cos
• tan

The three important ratios are:

Some people remember a well-known mnemonic using the first letters to help when deciding which ratio to use for each trig problem.

This mnemonic is:

SOH CAH TOA

These letters stand for:

S sine O opposite H hypotenuse

C cosine A adjacent H hypotenuse

T tangent O opposite A adjacent