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

NAME
       atanh, atanhf, atanhl - inverse hyperbolic tangent function

SYNOPSIS
       #include 

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

       Link with -lm.

   Feature Test Macro Requirements for glibc (see featuretestmacros(7)):

       atanh():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 500 ||
           XOPENSOURCE && XOPENSOURCEEXTENDED || ISOC99SOURCE ||
           POSIXCSOURCE >= 200112L;
           or cc -std=c99
       atanhf(), atanhl():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 ||
           ISOC99SOURCE || POSIXCSOURCE >= 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
       HUGEVAL, HUGEVALF, or HUGEVALL, 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 matherror(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
              (FEINVALID) 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 (FEDIVBYZERO) 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.  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)