atan2, atan2f, atan2l - arc tangent of x/y

Description atan2() computes the arc tangent of x/y, using the signs of both arguments to determine

Syntax	#include <math.h> double atan2(double x, double y); C11 float atan2f(float x, float y); long double atan2l(long double x, long double y);  (End)
Description	These functions compute the arc tangent of x/y, using the signs of both arguments to determine the quadrant of the return value. x is the dividend of the expression for which the arc tangent is to the calculated. y is the divisor of the expression for which the arc tangent is to the calculated.
Return val.	arc tangent(x/y)
		if neither argument is 0.0. A floating-point number of type double in the range [-pi/2, +pi/2] is returned.
	-pi/2 or +pi/2	if the divisor is 0.0, depending on the sign of the dividend.
	0 π/2	if the dividend is 0.0. if both arguments are 0.0. errno is set to indicate the error.
Errors	atan2(), atan2f() and atan2l() will fail if: EDOM        Both arguments are 0.0.
See also	acos(), asin(), atan(), cos(), sin(), tan(), math.h.