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>
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  26 .\"
  27 .\" References consulted:
  28 .\"     Linux libc source code
  29 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  30 .\"     386BSD man pages
  31 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  32 .\" Modified 2002-07-27 by Walter Harms
  33 .\"     (walter.harms@informatik.uni-oldenburg.de)
  34 .\"
  35 .TH ATANH 3  2017-09-15 "" "Linux Programmer's Manual"
  36 .SH NAME
  37 atanh, atanhf, atanhl \- inverse hyperbolic tangent function
  38 .SH SYNOPSIS
  39 .nf
  40 .B #include <math.h>
  41 .PP
  42 .BI "double atanh(double " x );
  43 .BI "float atanhf(float " x );
  44 .BI "long double atanhl(long double " x );
  45 .PP
  46 .fi
  47 Link with \fI\-lm\fP.
  48 .PP
  49 .in -4n
  50 Feature Test Macro Requirements for glibc (see
  51 .BR feature_test_macros (7)):
  52 .in
  53 .PP
  54 .ad l
  55 .BR atanh ():
  56 .RS 4
  57 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  58     || _XOPEN_SOURCE\ >=\ 500
  59 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  60     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  61     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  62 .RE
  63 .PP
  64 .BR atanhf (),
  65 .BR atanhl ():
  66 .RS 4
  67 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  68     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  69     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  70 .RE
  71 .ad b
  72 .SH DESCRIPTION
  73 These functions calculate the inverse hyperbolic tangent of
  74 .IR x ;
  75 that is the value whose hyperbolic tangent is
  76 .IR x .
  77 .SH RETURN VALUE
  78 On success, these functions return the inverse hyperbolic tangent of
  79 .IR x .
  80 .PP
  81 If
  82 .I x
  83 is a NaN, a NaN is returned.
  84 .PP
  85 If
  86 .I x
  87 is +0 (\-0), +0 (\-0) is returned.
  88 .PP
  89 If
  90 .I x
  91 is +1 or \-1,
  92 a pole error occurs,
  93 and the functions return
  94 .BR HUGE_VAL ,
  95 .BR HUGE_VALF ,
  96 or
  97 .BR HUGE_VALL ,
  98 respectively, with the mathematically correct sign.
  99 .PP
 100 If the absolute value of
 101 .I x
 102 is greater than 1,
 103 a domain error occurs,
 104 and a NaN is returned.
 105 .\"
 106 .\" POSIX.1-2001 documents an optional range error for subnormal x;
 107 .\" glibc 2.8 does not do this.
 108 .SH ERRORS
 109 See
 110 .BR math_error (7)
 111 for information on how to determine whether an error has occurred
 112 when calling these functions.
 113 .PP
 114 The following errors can occur:
 115 .TP
 116 Domain error: \fIx\fP less than \-1 or greater than +1
 117 .I errno
 118 is set to
 119 .BR EDOM .
 120 An invalid floating-point exception
 121 .RB ( FE_INVALID )
 122 is raised.
 123 .TP
 124 Pole error: \fIx\fP is +1 or \-1
 125 .I errno
 126 is set to
 127 .BR ERANGE
 128 (but see BUGS).
 129 A divide-by-zero floating-point exception
 130 .RB ( FE_DIVBYZERO )
 131 is raised.
 132 .SH ATTRIBUTES
 133 For an explanation of the terms used in this section, see
 134 .BR attributes (7).
 135 .TS
 136 allbox;
 137 lbw28 lb lb
 138 l l l.
 139 Interface       Attribute       Value
 140 T{
 141 .BR atanh (),
 142 .BR atanhf (),
 143 .BR atanhl ()
 144 T}      Thread safety   MT-Safe
 145 .TE
 146 .SH CONFORMING TO
 147 C99, POSIX.1-2001, POSIX.1-2008.
 148 .PP
 149 The variant returning
 150 .I double
 151 also conforms to
 152 SVr4, 4.3BSD.
 153 .SH BUGS
 154 In glibc 2.9 and earlier,
 155 .\" Bug: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759
 156 .\" This can be seen in sysdeps/ieee754/k_standard.c
 157 when a pole error occurs,
 158 .I errno
 159 as set to
 160 .BR EDOM
 161 instead of the POSIX-mandated
 162 .BR ERANGE .
 163 Since version 2.10, glibc does the right thing.
 164 .SH SEE ALSO
 165 .BR acosh (3),
 166 .BR asinh (3),
 167 .BR catanh (3),
 168 .BR cosh (3),
 169 .BR sinh (3),
 170 .BR tanh (3)