Guide to Game Development/Theory/Mathematics/Trigonometry/The basic identities applied to right angle triangles

Opposite, Adjacent and Hypotenuse
When you have a right-angled triangle, and you decide on one of the 2 non-right-angled angles, you can then decide on what the names of the sides are.

Soh Cah Toa
Soh Cah Toa is an acronym to help you remember how you can use your knowledge of opposites, adjacents and hypotenuses to find extra pieces of information on a right-angled triangle. Written out as three equations, it looks like:

$$\sin(\theta) = \frac{Opposite}{Hypotenuse}$$

$$\cos(\theta) = \frac{Adjacent}{Hypotenuse}$$

$$\tan(\theta) = \frac{Opposite}{Adjacent}$$

Using these three equations, if you were given two pieces of information (as long as they're both NOT angles), you can any other piece of information on the triangle. Note: the Greek letter, $$\theta$$ is often used with angles to mean, "an unknown angle."

Inverse trigonometry
There are three main inverse trigonometric functions: $$\sin ^{-1}, \cos ^{-1}$$ and $$\tan ^{-1}$$.