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  2016-03-15 "" "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 .sp
  42 .BI "double atanh(double " x );
  43 .br
  44 .BI "float atanhf(float " x );
  45 .br
  46 .BI "long double atanhl(long double " x );
  47 .sp
  48 .fi
  49 Link with \fI\-lm\fP.
  50 .sp
  51 .in -4n
  52 Feature Test Macro Requirements for glibc (see
  53 .BR feature_test_macros (7)):
  54 .in
  55 .sp
  56 .ad l
  57 .BR atanh ():
  58 .RS 4
  59 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  60     || _XOPEN_SOURCE\ >=\ 500
  61 .\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  62     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  63     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  64 .RE
  65
  66 .BR atanhf (),
  67 .BR atanhl ():
  68 .RS 4
  69 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  70     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  71     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  72 .RE
  73 .ad b
  74 .SH DESCRIPTION
  75 These functions calculate the inverse hyperbolic tangent of
  76 .IR x ;
  77 that is the value whose hyperbolic tangent is
  78 .IR x .
  79 .SH RETURN VALUE
  80 On success, these functions return the inverse hyperbolic tangent of
  81 .IR x .
  82
  83 If
  84 .I x
  85 is a NaN, a NaN is returned.
  86
  87 If
  88 .I x
  89 is +0 (\-0), +0 (\-0) is returned.
  90
  91 If
  92 .I x
  93 is +1 or \-1,
  94 a pole error occurs,
  95 and the functions return
  96 .BR HUGE_VAL ,
  97 .BR HUGE_VALF ,
  98 or
  99 .BR HUGE_VALL ,
 100 respectively, with the mathematically correct sign.
 101
 102 If the absolute value of
 103 .I x
 104 is greater than 1,
 105 a domain error occurs,
 106 and a NaN is returned.
 107 .\"
 108 .\" POSIX.1-2001 documents an optional range error for subnormal x;
 109 .\" glibc 2.8 does not do this.
 110 .SH ERRORS
 111 See
 112 .BR math_error (7)
 113 for information on how to determine whether an error has occurred
 114 when calling these functions.
 115 .PP
 116 The following errors can occur:
 117 .TP
 118 Domain error: \fIx\fP less than \-1 or greater than +1
 119 .I errno
 120 is set to
 121 .BR EDOM .
 122 An invalid floating-point exception
 123 .RB ( FE_INVALID )
 124 is raised.
 125 .TP
 126 Pole error: \fIx\fP is +1 or \-1
 127 .I errno
 128 is set to
 129 .BR ERANGE
 130 (but see BUGS).
 131 A divide-by-zero floating-point exception
 132 .RB ( FE_DIVBYZERO )
 133 is raised.
 134 .SH ATTRIBUTES
 135 For an explanation of the terms used in this section, see
 136 .BR attributes (7).
 137 .TS
 138 allbox;
 139 lbw28 lb lb
 140 l l l.
 141 Interface       Attribute       Value
 142 T{
 143 .BR atanh (),
 144 .BR atanhf (),
 145 .BR atanhl ()
 146 T}      Thread safety   MT-Safe
 147 .TE
 148 .SH CONFORMING TO
 149 C99, POSIX.1-2001, POSIX.1-2008.
 150
 151 The variant returning
 152 .I double
 153 also conforms to
 154 SVr4, 4.3BSD.
 155 .SH BUGS
 156 In glibc 2.9 and earlier,
 157 .\" Bug: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6759
 158 .\" This can be seen in sysdeps/ieee754/k_standard.c
 159 when a pole error occurs,
 160 .I errno
 161 as set to
 162 .BR EDOM
 163 instead of the POSIX-mandated
 164 .BR ERANGE .
 165 Since version 2.10, glibc does the right thing.
 166 .SH SEE ALSO
 167 .BR acosh (3),
 168 .BR asinh (3),
 169 .BR catanh (3),
 170 .BR cosh (3),
 171 .BR sinh (3),
 172 .BR tanh (3)