Sin, Cos, Rep

Sin. What does it do?
Cos. What does it do?
Rep. Will be given.

Sin and Cos are used for movement calculation (mainly) due they got the power to translate an angle into an vector.
However i think wikipedia can explain it more detailed than me with my lousy english.
But i still will try it.
Let's say we got a circle with r = 50 and you want to move a unit somewhere on the circle boarder (i hope this is the correct word) then you need 2 components.
The x and the y value of the target location.
With the help of Sin we can calculated the y-Value.
y = CircleCenterY + Sin(angle) * r
The same also applies for the x value and Cos.
x = CircleCenterX + Cos(angle) * r
I think these are the main reasons of using Cos / sin, a simple vector calculation...

https://webfiles.berkeley.edu/p_d/doc/keyofe/

(10) is your definition for cosine and sine. The pages before explain what it means: the x,y coordinates of a point on a circle parameterized by the distance along the circle counterclockwise from the right most point. The rest explains how you can calculate and simplify expressions with sin/cos.

I understood Fireeye more, but you both get rep

Tan is also the same sort of thing.

Here are the triangle things for them:

-O --A --O
SxH CxH TxA


S=Sine
C=Cosine
T=Tangent
O=Opposite
A=Adjacent
H=Hypotenuse