S O H C A H T O A

There are three main functions in trigonometry and they are sine (sin), cosine (cos) and tangent (tan). These three main functions help us find a missing side or angle. Sine, cosine and tangent are all based on a right-angled triangle. 

For a right-angled triangle with a given angle θ, the three main functions sine, cosine and tangent are given by:

sine of an angle θ = Opposite / Hypotenuse

cosine of an angle θ = Adjacent / Hypotenuse

tangent of an angle θ = Opposite / Adjacent

SOHCAHTOA is a useful way of remembering the three main functions.

- k.v.