Trigonometry:

Trigonometry is used to work out the unknown angles and sides on a right angled triangle.
The easy way to remember it is SOH CAH TOA
If you want to work out an angle and you have either the side opposite it or the hypotenuse, you use sine(theta) = O/H
The same could be used to work out one of the sides if you already have the angle.
If you want to work out an angle and you have either the side adjacent to it or the hypotenuse, you use cosine(theta) = A/H
If you want to work out an angle and you have either the side opposite it or the adjacent, you use tangent(theta) = O/A

Example:

A right angle triangle has a hypotenuse of 5cm and the side opposite the angle is 3cm.
You would do sin⁻ⁱ(theta) = 3/5 = 63

By Muhammed