C++ In a Nutshell

Name

atan2 function — Computes inverse tangent

Synopsis

float atan2(float y, float x)
double atan2(double y, double x)
long double atan2(long double y, long double x)

The atan2 function returns the inverse tangent of y/x using the sign of both numbers to determine the quadrant for the return value. It correctly handles the case in which x is 0. (That is, it returns π/2 times the sign of y for nonzero y; if y is 0, the result is implementation-defined and might be a range error). The return value is in the range [-π, π].