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: /**/