Trigonometry is a branch of mathematics that describes the relationships between the length of the sides and angles of triangles. It might not seem obvious but this type of maths is utilised in alternating current theory.

The three trigonometric ratios we will be looking at are: Sine, Cosine and Tangent which are abbreviated to SIN, COS and TAN respectiviely.

Using "SOHCAHTOA" is a way of reminding your self of the ratios.

Here are some examples of the use of trigonometry. For each of the triangles only an angle and a length of only one side is given. When tackling this you need to think about which ratio you need to use, and for this SOHCAHTOA is very useful.

When two sides are known an unknown angle can be calculated, This is achieved by using the inverse functions of SIN, COS and TAN.