man3/tan.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 TAN 3 2017-09-15 ""  "Linux Programmer's Manual"
  36 .SH NAME
  37 tan, tanf, tanl \- tangent function
  38 .SH SYNOPSIS
  39 .nf
  40 .B #include <math.h>
  41 .PP
  42 .BI "double tan(double " x );
  43 .BI "float tanf(float " x );
  44 .BI "long double tanl(long double " x );
  45 .fi
  46 .PP
  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 tanf (),
  56 .BR tanl ():
  57 .RS 4
  58 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  59     || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  60     || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  61 .RE
  62 .ad
  63 .SH DESCRIPTION
  64 These functions return the tangent of
  65 .IR x ,
  66 where
  67 .I x
  68 is
  69 given in radians.
  70 .SH RETURN VALUE
  71 On success, these functions return the tangent of
  72 .IR x .
  73 .PP
  74 If
  75 .I x
  76 is a NaN, a NaN is returned.
  77 .PP
  78 If
  79 .I x
  80 is positive infinity or negative infinity,
  81 a domain error occurs,
  82 and a NaN is returned.
  83 .PP
  84 If the correct result would overflow,
  85 a range error occurs,
  86 and the functions return
  87 .BR HUGE_VAL ,
  88 .BR HUGE_VALF ,
  89 or
  90 .BR HUGE_VALL ,
  91 respectively, with the mathematically correct sign.
  92 .\" I think overflow can't occur, because the closest floating-point
  93 .\" representation of pi/2 is still not close enough to pi/2 to
  94 .\" produce a large enough value to overflow.
  95 .\" Testing certainly seems to bear this out.  -- mtk, Jul 08
  96 .\"
  97 .\" POSIX.1 allows an optional underflow error;
  98 .\" glibc 2.8 doesn't do this
  99 .\" POSIX.1 an optional range error for subnormal x;
 100 .\" glibc 2.8 doesn't do this
 101 .SH ERRORS
 102 See
 103 .BR math_error (7)
 104 for information on how to determine whether an error has occurred
 105 when calling these functions.
 106 .PP
 107 The following errors can occur:
 108 .TP
 109 Domain error: \fIx\fP is an infinity
 110 .I errno
 111 is set to
 112 .BR EDOM
 113 (but see BUGS).
 114 An invalid floating-point exception
 115 .RB ( FE_INVALID )
 116 is raised.
 117 .TP
 118 Range error: result overflow
 119 .\" Unable to test this case, since the best approximation of
 120 .\" pi/2 in double precision only yields a tan() value of 1.633e16.
 121 .\" .I errno
 122 .\" is set to
 123 .\" .BR ERANGE .
 124 An overflow floating-point exception
 125 .RB ( FE_OVERFLOW )
 126 is raised.
 127 .SH ATTRIBUTES
 128 For an explanation of the terms used in this section, see
 129 .BR attributes (7).
 130 .TS
 131 allbox;
 132 lbw21 lb lb
 133 l l l.
 134 Interface       Attribute       Value
 135 T{
 136 .BR tan (),
 137 .BR tanf (),
 138 .BR tanl ()
 139 T}      Thread safety   MT-Safe
 140 .TE
 141 .SH CONFORMING TO
 142 C99, POSIX.1-2001, POSIX.1-2008.
 143 .PP
 144 The variant returning
 145 .I double
 146 also conforms to
 147 SVr4, 4.3BSD, C89.
 148 .SH BUGS
 149 Before version 2.10, the glibc implementation did not set
 150 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=6782
 151 .I errno
 152 to
 153 .B EDOM
 154 when a domain error occurred.
 155 .SH SEE ALSO
 156 .BR acos (3),
 157 .BR asin (3),
 158 .BR atan (3),
 159 .BR atan2 (3),
 160 .BR cos (3),
 161 .BR ctan (3),
 162 .BR sin (3)