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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():
         _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  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.

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.

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.