atan(3M)

NAME

     atan - arc tangent function

SYNOPSIS

     cc [ flag ... ] file ... -lm [ library ... ]
     #include <math.h>

     double atan(double x);

DESCRIPTION

     The atan() function computes the principal value of the  arc
     tangent of x.

RETURN VALUES

     Upon successful completion, atan() returns the  arc  tangent
     of x in the range [-pi/2,pi/2] radians.

     If x is NaN, NaN is returned.

     If x is _Inf, _pi/2 is returned.

ERRORS

     No errors will occur.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|

SEE ALSO

     atan2(3M), isnan(3M), tan(3M), attributes(5)