Inverse of math.atan2?

Apparently, something like this will help:

x = cos(theta)
y = sin(theta) 

Simple Google search threw this up, and the guy who asked the question said it solved it.

Given only the angle you can only derive a unit vector pointing to (dx, dy). To get the original (dx, dy) you also need to know the length of the vector (dx, dy), which I'll call len. You also have to convert the angle you derived from degrees back to radians and then use the trig equations mentioned elsewhere in this post. That is you have:

local dy = y1-y2
local dx = x1-x2
local angle = atan2(dy,dx) * 180 / pi
local len = sqrt(dx*dx + dy*dy)

Given angle (in degrees) and the vector length, len, you can derive dx and dy by:

local theta = angle * pi / 180
local dx = len * cos(theta)
local dy = len * sin(theta)