man3/atanh.3

   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>
   4 .\"
   5 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   6 .\"
   7 .\" References consulted:
   8 .\"     Linux libc source code
   9 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  10 .\"     386BSD man pages
  11 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  12 .\" Modified 2002-07-27 by Walter Harms
  13 .\"     (walter.harms@informatik.uni-oldenburg.de)
  14 .\"
  15 .TH ATANH 3  2021-03-22 "" "Linux Programmer's Manual"
  16 .SH NAME
  17 atanh, atanhf, atanhl \- inverse hyperbolic tangent function
  18 .SH LIBRARY
  19 Math library
  20 .RI ( libm ", " \-lm )
  21 .SH SYNOPSIS
  22 .nf
  23 .B #include <math.h>
  24 .PP
  25 .BI "double atanh(double " x );
  26 .BI "float atanhf(float " x );
  27 .BI "long double atanhl(long double " x );
  28 .PP
  29 .fi
  30 .RS -4
  31 Feature Test Macro Requirements for glibc (see
  32 .BR feature_test_macros (7)):
  33 .RE
  34 .PP
  35 .BR atanh ():
  36 .nf
  37     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  38         || _XOPEN_SOURCE >= 500
  39 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  40         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  41         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  42 .fi
  43 .PP
  44 .BR atanhf (),
  45 .BR atanhl ():
  46 .nf
  47     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  48         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  49         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  50 .fi
  51 .SH DESCRIPTION
  52 These functions calculate the inverse hyperbolic tangent of
  53 .IR x ;
  54 that is the value whose hyperbolic tangent is
  55 .IR x .
  56 .SH RETURN VALUE
  57 On success, these functions return the inverse hyperbolic tangent of
  58 .IR x .
  59 .PP
  60 If
  61 .I x
  62 is a NaN, a NaN is returned.
  63 .PP
  64 If
  65 .I x
  66 is +0 (\-0), +0 (\-0) is returned.
  67 .PP
  68 If
  69 .I x
  70 is +1 or \-1,
  71 a pole error occurs,
  72 and the functions return
  73 .BR HUGE_VAL ,
  74 .BR HUGE_VALF ,
  75 or
  76 .BR HUGE_VALL ,
  77 respectively, with the mathematically correct sign.
  78 .PP
  79 If the absolute value of
  80 .I x
  81 is greater than 1,
  82 a domain error occurs,
  83 and a NaN is returned.
  84 .\"
  85 .\" POSIX.1-2001 documents an optional range error for subnormal x;
  86 .\" glibc 2.8 does not do this.
  87 .SH ERRORS
  88 See
  89 .BR math_error (7)
  90 for information on how to determine whether an error has occurred
  91 when calling these functions.
  92 .PP
  93 The following errors can occur:
  94 .TP
  95 Domain error: \fIx\fP less than \-1 or greater than +1
  96 .I errno
  97 is set to
  98 .BR EDOM .
  99 An invalid floating-point exception
 100 .RB ( FE_INVALID )
 101 is raised.
 102 .TP
 103 Pole error: \fIx\fP is +1 or \-1
 104 .I errno
 105 is set to
 106 .BR ERANGE
 107 (but see BUGS).
 108 A divide-by-zero floating-point exception
 109 .RB ( FE_DIVBYZERO )
 110 is raised.
 111 .SH ATTRIBUTES
 112 For an explanation of the terms used in this section, see
 113 .BR attributes (7).
 114 .ad l
 115 .nh
 116 .TS
 117 allbox;
 118 lbx lb lb
 119 l l l.
 120 Interface       Attribute       Value
 121 T{
 122 .BR atanh (),
 123 .BR atanhf (),
 124 .BR atanhl ()
 125 T}      Thread safety   MT-Safe
 126 .TE
 127 .hy
 128 .ad
 129 .sp 1
 130 .SH CONFORMING TO
 131 C99, POSIX.1-2001, POSIX.1-2008.
 132 .PP
 133 The variant returning
 134 .I double
 135 also conforms to
 136 SVr4, 4.3BSD.
 137 .SH BUGS
 138 In glibc 2.9 and earlier,
 139 .\" Bug: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759
 140 .\" This can be seen in sysdeps/ieee754/k_standard.c
 141 when a pole error occurs,
 142 .I errno
 143 is set to
 144 .BR EDOM
 145 instead of the POSIX-mandated
 146 .BR ERANGE .
 147 Since version 2.10, glibc does the right thing.
 148 .SH SEE ALSO
 149 .BR acosh (3),
 150 .BR asinh (3),
 151 .BR catanh (3),
 152 .BR cosh (3),
 153 .BR sinh (3),
 154 .BR tanh (3)