atanh(3)                   Library Functions Manual                   atanh(3)

NAME
       atanh, atanhf, atanhl - inverse hyperbolic tangent function

LIBRARY
       Math library (libm, -lm)

SYNOPSIS
       #include <math.h>

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

   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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       atanhf(), atanhl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 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 |
       +--------------------------------------------+---------------+---------+
STANDARDS
       C11, POSIX.1-2008.

HISTORY
       C99, POSIX.1-2001.

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

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

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

Linux man-pages 6.7               2023-10-31                          atanh(3)