In a right-angled triangle, the sides and the angles are connected by three trigonometric ratios.

The three trig ratios are:

A quick way to remember this is to memorise the word

SOHCAHTOA

Example

Which trigonometric ratio is used to calculate the angle θº ?

Answer

Label the sides adjacent, opposite and hypotenuse in relation to the angle θº.

The given sides are the adjacent and the hypotenuse.

SOHCAHTOA

The correct trig ratio is COS.