man3/tanh.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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  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 TANH 3 2015-04-19 ""  "Linux Programmer's Manual"
  36 .SH NAME
  37 tanh, tanhf, tanhl \- hyperbolic tangent function
  38 .SH SYNOPSIS
  39 .nf
  40 .B #include <math.h>
  41 .sp
  42 .BI "double tanh(double " x );
  43 .br
  44 .BI "float tanhf(float " x );
  45 .br
  46 .BI "long double tanhl(long double " x );
  47 .fi
  48 .sp
  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 tanhf (),
  58 .BR tanhl ():
  59 .RS 4
  60 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  61     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  62     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  63 .br
  64 or
  65 .I cc\ -std=c99
  66 .RE
  67 .ad
  68 .SH DESCRIPTION
  69 These functions return the hyperbolic tangent of
  70 .IR x ,
  71 which
  72 is defined mathematically as:
  73 .nf
  74
  75     tanh(x) = sinh(x) / cosh(x)
  76 .fi
  77 .SH RETURN VALUE
  78 On success, these functions return the hyperbolic tangent of
  79 .IR x .
  80
  81 If
  82 .I x
  83 is a NaN, a NaN is returned.
  84
  85 If
  86 .I x
  87 is +0 (\-0), +0 (\-0) is returned.
  88
  89 If
  90 .I x
  91 is positive infinity (negative infinity),
  92 +1 (\-1) is returned.
  93 .\"
  94 .\" POSIX.1-2001 documents an optional range error (underflow)
  95 .\" for subnormal x;
  96 .\" glibc 2.8 does not do this.
  97 .SH ERRORS
  98 No errors occur.
  99 .SH ATTRIBUTES
 100 For an explanation of the terms used in this section, see
 101 .BR attributes (7).
 102 .TS
 103 allbox;
 104 lbw24 lb lb
 105 l l l.
 106 Interface       Attribute       Value
 107 T{
 108 .BR tanh (),
 109 .BR tanhf (),
 110 .BR tanhl ()
 111 T}      Thread safety   MT-Safe
 112 .TE
 113 .SH CONFORMING TO
 114 C99, POSIX.1-2001, POSIX.1-2008.
 115
 116 The variant returning
 117 .I double
 118 also conforms to
 119 SVr4, 4.3BSD, C89.
 120 .SH SEE ALSO
 121 .BR acosh (3),
 122 .BR asinh (3),
 123 .BR atanh (3),
 124 .BR cosh (3),
 125 .BR ctanh (3),
 126 .BR sinh (3)