atan - arc tangent function


SYNOPSIS

       #include <math.h>

       double atan(double x);


DESCRIPTION

       The  atan() function calculates the arc tangent of x; that
       is the value whose tangent is x.


RETURN VALUE

       The atan() function returns the arc tangent in radians and
       the  value  is  mathematically defined to be between -PI/2
       and PI/2 (inclusive).


CONFORMING TO

       SVID 3, POSIX, BSD 4.3, ISO 9899


SEE ALSO

       acos(3), asin(3), atan2(3), cos(3), sin(3), tan(3)