soh cah toa

You use cos (cosign) sin (sine) and tan (tangent) to find the lengths of sides of triangles.

Also, you press these buttons on a calculator to use them:

Sine is $\frac{opposite}{hypotenuse}$

Cosine is $\frac{adjacent}{hypotenuse}$

Tangent is $\frac{opposite}{hypotenuse}$