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[thirdparty/man-pages.git] / man3 / atanh.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
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.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.TH ATANH 3  2015-04-19 "" "Linux Programmer's Manual"
.SH NAME
atanh, atanhf, atanhl \- inverse hyperbolic tangent function
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double atanh(double " x );
.br
.BI "float atanhf(float " x );
.br
.BI "long double atanhl(long double " x );
.sp
.fi
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR atanh ():
.RS 4
_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
    || _XOPEN_SOURCE\ >=\ 500
.\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE

.BR atanhf (),
.BR atanhl ():
.RS 4
_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.ad b
.SH DESCRIPTION
These functions calculate the inverse hyperbolic tangent of
.IR x ;
that is the value whose hyperbolic tangent is
.IR x .
.SH RETURN VALUE
On success, these functions return the inverse hyperbolic tangent of
.IR x .

If
.I x
is a NaN, a NaN is returned.

If
.I x
is +0 (\-0), +0 (\-0) is returned.

If
.I x
is +1 or \-1,
a pole error occurs,
and the functions return
.BR HUGE_VAL ,
.BR HUGE_VALF ,
or
.BR HUGE_VALL ,
respectively, with the mathematically correct sign.

If the absolute value of
.I x
is greater than 1,
a domain error occurs,
and a NaN is returned.
.\"
.\" POSIX.1-2001 documents an optional range error for subnormal x;
.\" glibc 2.8 does not do this.
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.PP
The following errors can occur:
.TP
Domain error: \fIx\fP less than \-1 or greater than +1
.I errno
is set to
.BR EDOM .
An invalid floating-point exception
.RB ( FE_INVALID )
is raised.
.TP
Pole error: \fIx\fP is +1 or \-1
.I errno
is set to
.BR ERANGE
(but see BUGS).
A divide-by-zero floating-point exception
.RB ( FE_DIVBYZERO )
is raised.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw28 lb lb
l l l.
Interface	Attribute	Value
T{
.BR atanh (),
.BR atanhf (),
.BR atanhl ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.

The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH BUGS
In glibc 2.9 and earlier,
.\" Bug: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759
.\" This can be seen in sysdeps/ieee754/k_standard.c
when a pole error occurs,
.I errno
as set to
.BR EDOM
instead of the POSIX-mandated
.BR ERANGE .
Since version 2.10, glibc does the right thing.
.SH SEE ALSO
.BR acosh (3),
.BR asinh (3),
.BR catanh (3),
.BR cosh (3),
.BR sinh (3),
.BR tanh (3)