# Basic Facts

## Basic Facts

The word 'Trigonometry' seems to strike dread into people (a bit like the word 'Algebra') but if you learn a few starting facts and a few equations,that's all there is to it - well, almost!

#### Right-angled triangles

Trigonometry at GCSE is almost all concerned with right-angled triangles (unless you're doing 'Higher').

First you must know how to label a triangle:

For Pythagoras' Theorem we simply label the sides a, b and c (with c being the side opposite the right-angle).

#### Hypotenuse, Adjacent and Opposite

For a particular angle, the sides also have names:

The longest side (opposite the right-angle) is called the Hypotenuse.

The side next to the angle is called the Adjacent (which means 'next-to').

The side opposite the angle is called the Opposite (for obvious reasons!).

Obviously, if you are looking at the other angle the names of the sides move accordingly!

Below is a quick test to make sure you have got the idea. Drag the labels onto the correct place and mark your answer: