Trigonometric ratios: SOH CAH TOA

In a nutshell

Trigonometric ratios allow you to find a length or angle of a right-angled triangle. To do so, you need to know how to label one.

Label	Meaning
$x$	The angle you're focusing on (you will either have to find out the value of $x$ or use it to find the length of a side)
Hypotenuse	The longest side of the triangle
Opposite	The side opposite the angle labelled $x$
Adjacent	The side next to the labelled angle that isn't the hypotenuse

These are the 3 main functions and their ratios:

Function name	Found on your calculator as	Corresponding ratio	Simplified version
Sine	$\sin()$	$\sin(x)=\frac{opposite}{hypotenuse}$	SOH
Cosine	$\cos()$	$\cos(x)=\frac{adjacent}{hypotenuse}$	CAH
Tangent	$\tan()$	$\tan(x)=\frac{opposite}{adjacent}$	TOA

Note: It is common and easy to just remember these three as SOH CAH TOA.