arctangent is like arccosine and arcsine.

It's called arc because of the unit circle but there's another name for it I forget what it's like anti ___ I think.

Anyway say I have a number like:

right?

So

Arctangent is the same:

say I'm looking at:

It's just the opposite of what tangent does, you stuff an angle into tangent, and you get a ratio. For arctan/arcsin/arcos you stuff the ratio and it spits out the angle for that ratio.