atan2

atan2, atan2f, atan2l - arc tangent function of two variables

#include <math.h>
 I double atan2(double  y , double  x );

I float atan2f(float  y , float  x );

I long double atan2l(long double  y , long double  x );
 

Link with -lm.

The R atan2 () function calculates the arc tangent of the two variables x and y. It is similar to calculating the arc tangent of y / x, except that the signs of both arguments are used to determine the quadrant of the result.

The R atan2 () function returns the result in radians, which is between -PI and PI (inclusive).

SVr4, POSIX.1-2001, 4.3BSD, C89. The float and long double variants are C99 requirements.

acos(3), asin(3), atan(3), cos(3), sin(3), tan(3)