ATANH(3)		   Linux Programmers Manual		     ATANH(3)



NAME
       atanh, atanhf, atanhl - inverse hyperbolic tangent function

SYNOPSIS
       #include 

       double atanh(double x);
       float atanhf(float x);
       long double atanhl(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       atanh(), atanhf(), atanhl(): _BSD_SOURCE || _SVID_SOURCE ||
       _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION
       The atanh() function calculates the inverse hyperbolic  tangent	of  x;
       that is the value whose hyperbolic tangent is x.  If the absolute value
       of x is greater than 1.0, atanh() returns not-a-number (NaN) and  errno
       is set.

ERRORS
       EDOM   x is out of range.

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

SEE ALSO
       acosh(3), asinh(3), catanh(3), cosh(3), sinh(3), tanh(3)

COLOPHON
       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



				  2007-07-26			      ATANH(3)