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

USAGE
       #include <math.h>

       double atan2(double y, double x);
       float atan2f(float y, float x);
       long double atan2l(long double y, long double x);

       Link with -lm.

DESCRIPTION
       The  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.

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

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

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