Trigonometry: what is it, and how do I do it?

Trigonometry is used in maths to find angles and the lengths of edges in triangles. There are three main operations: sin, cos and tan, and these are used to convert the information you have about a triangle, into the information you need to know for the answer.

For a simple trig question, you need to start with three things: a right-angled triangle, and the lengths of two of the sides. You can then select your operation based on what information you have, and their location relating to the angle you’re trying to work out. To use sin, you need the opposite edge and the hypotenuse. For cos, the adjacent edge and the hypotenuse and for tan, the opposite and adjacent edges. (The hypotenuse is the length of the longest side, opposite the right angle).

To find a given angle, you divide the first length by the second, and then do the operation on this number.

The mnemonic SOHCAHTOA is useful to remember to tell you which operation to use, and which length to divide by which.