1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
30 .\" Modified 2002-07-27 by Walter Harms
31 .\" (walter.harms@informatik.uni-oldenburg.de)
33 .TH ATANH 3 2008-08-05 "" "Linux Programmer's Manual"
35 atanh, atanhf, atanhl \- inverse hyperbolic tangent function
40 .BI "double atanh(double " x );
42 .BI "float atanhf(float " x );
44 .BI "long double atanhl(long double " x );
50 Feature Test Macro Requirements for glibc (see
51 .BR feature_test_macros (7)):
56 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
61 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
67 function calculates the inverse hyperbolic tangent of
68 \fIx\fP; that is the value whose hyperbolic tangent is \fIx\fP.
70 On success, these functions return the inverse hyperbolic tangent of
75 is a NaN, a NaN is returned.
79 is +0 (\-0), +0 (\-0) is returned.
85 and the functions return
90 respectively, with the mathematically correct sign.
92 If the absolute value of
95 a domain error occurs,
96 and a NaN is returned.
98 .\" POSIX.1-2001 documents an optional range error for subnormal x;
99 .\" glibc 2.8 does not do this.
103 for information on how to determine whether an error has occurred
104 when calling these functions.
106 The following errors can occur:
108 Domain error: \fIx\fP less than \-1 or greater than +1
112 An invalid floating-point exception
116 Pole error: \fIx\fP is +1 or \-1
121 .\" FIXME . glibc actually gives EDOM for this case
122 A divide-by-zero floating-point exception
127 The variant returning
134 .\" FIXME . this is as at glibc 2.8; check later if this bug is fixed
135 .\" This can be seen in sysdeps/ieee754/k_standard.c
136 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759
140 POSIX.1 says it should be set to