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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 ||
           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99
       atanhf(), atanhl():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           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, respectively,  with  the  mathemati-
       cally 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  float-
              ing-point exception (FE_DIVBYZERO) is raised.
CONFORMING TO
       C99, POSIX.1-2001.  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 3.53 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/.

                                  2010-09-11                          ATANH(3)