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

Definition	#include <math.h> double atan2(double x, double y);float atanf(float x); (C11) long double atanl(long double x); (C11) These functions calculate the arc tangent of x/y. The signs of the two arguments determine the resulting quadrants.
Return val.	arc tangent(x/y)
		a floating-point number of type double in the interval [-pi/2, +pi/2]. If the divisor y is equal to 0, atan2 returns either -pi/2 or +pi/2, depending on the sign of the dividend.
	0	if the dividend x is equal to 0.
	pi/2	if both arguments are equal to 0. errno is set to EDOM (domain error).
Example	The following program reads in the arguments x and y and prints the computed arc tangent of x/y. #include <math.h> #include <stdio.h> int main(void) { double x, y; printf("Example of ATAN2(x/y)\n"); printf("Enter x and y please:\n"); if (scanf("%lf %lf", &x, &y) == 2) printf("ATAN2 (%g / %g) = %g\n", x, y, atan2(x, y)); return 0; }
See also	atan, tan, sin, asin, cos, acos