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),