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# Basic Facts

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## 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!

**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).

**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:**