Simple trigonometry can be used with right angled triangles to find an angle given two sides, or a side given a side and one of the interior angles other than the right angle,

With the sides of the triangle as labelled above, we can use one of the formulae:

Example: Finding an angle using cos

For the triangle above, we haveandand want to findThis means we use

Example: Finding an angle using tan

For the triangle above, we haveandand want to find This means we use

Example: Finding an angle using sin

For the triangle above, we haveandand want to find This means we use