Open Source Software

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():
       _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
           || _XOPEN_SOURCE >= 500
           || /* Since glibc 2.19: */ _DEFAULT_SOURCE
           || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

   atanhf(), atanhl():
       _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
           || /* Since glibc 2.19: */ _DEFAULT_SOURCE
           || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

   These  functions calculate 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,   respectively,   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 functions.

   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  (but  see  BUGS).   A divide-by-zero
          floating-point exception (FE_DIVBYZERO) is raised.

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   
   Interface                     Attribute      Value   
   
   atanh(), atanhf(), atanhl()   Thread safety  MT-Safe

CONFORMING TO

   C99, POSIX.1-2001, POSIX.1-2008.

   The variant returning double also conforms to SVr4, 4.3BSD, C89.

BUGS

   In  glibc  2.9  and  earlier, when a pole error occurs, errno as set to
   EDOM instead of the POSIX-mandated ERANGE.  Since version  2.10,  glibc
   does the right thing.

SEE ALSO

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

COLOPHON

   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at
   https://www.kernel.org/doc/man-pages/.

                              2016-03-15                          ATANH(3)



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