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ATANH(3)                   Linux Programmer's Manual                  ATANH(3)



NAME
       atanh, atanhf, atanhl - inverse hyperbolic tangent function

SYNOPSIS
       #include <math.h>

       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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99
       atanhf(), atanhl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _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.

RETURN VALUE
       On success, these functions return the inverse hyperbolic tangent of x.

       If x is a NaN, a NaN is returned.

       If x is +0 (-0), +0 (-0) is returned.

       If x is +1 or -1, a pole error occurs, and the functions return  HUGE_VAL,  HUGE_VALF,  or  HUGE_VALL,  respec-
       tively, with the mathematically correct sign.

       If the absolute value of x is greater than 1, a domain error occurs, and a NaN is returned.

ERRORS
       See  math_error(7)  for  information on how to determine whether an error has occurred when calling these func-
       tions.

       The following errors can occur:

       Domain error: x less than -1 or greater than +1
              errno is set to EDOM.  An invalid floating-point exception (FE_INVALID) is raised.

       Pole error: x is +1 or -1
              errno is set to ERANGE.  A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.

CONFORMING TO
       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4, 4.3BSD, C89.

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

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2008-08-05                          ATANH(3)