Trigonometry is a branch of mathematics that deals with angles and triangles and functions.

There are 6 basic functions that are included in trigonometry. Sine, cosine, tangent, cotangent, secant, cosecant.

The opposite side is the side facing the angle  θ, adjacent is the side that's shorter but the angles touches, hypotenuse is the longest side or the slant.

after you know the trig result or like cos=adjacent/hypotenuse=a, what is theta, or the angle you're trying to get?

That's when we do the inverses of trig functions:

Below is a list of trig identities:

Explanation: In the laws of sines and cosines, the uppercase letters are the angles and the lower case letters are the side lengths of a triangle. The uppercase letters' opposite side is their corresponding lower case letter.

Below is a trig chart to help memorization:

Real life visuals: