Inverse of math.atan2?

Question

What is the inverse of the function

math.atan2

I use this in Lua where I can get the inverse of math.atan by math.tan

Answer 1

According this reference:

Returns the arc tangent of y/x (in radians), but uses the signs of both parameters to find the quadrant of the result. (It also handles correctly the case of x being zero.)

So I guess you can use math.tan to invert it also.