ATAN(3)

NAME
       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)