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 2015-03-02 ""  "Linux Programmer's Manual"
  36 .SH NAME
  37 tan, tanf, tanl \- tangent function
  38 .SH SYNOPSIS
  39 .nf
  40 .B #include <math.h>
  41 .sp
  42 .BI "double tan(double " x );
  43 .br
  44 .BI "float tanf(float " x );
  45 .br
  46 .BI "long double tanl(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 tanf (),
  58 .BR tanl ():
  59 .RS 4
  60 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
  61 _POSIX_C_SOURCE\ >=\ 200112L;
  62 .br
  63 or
  64 .I cc\ -std=c99
  65 .RE
  66 .ad
  67 .SH DESCRIPTION
  68 These functions return the tangent of
  69 .IR x ,
  70 where
  71 .I x
  72 is
  73 given in radians.
  74 .SH RETURN VALUE
  75 On success, these functions return the tangent of
  76 .IR x .
  77
  78 If
  79 .I x
  80 is a NaN, a NaN is returned.
  81
  82 If
  83 .I x
  84 is positive infinity or negative infinity,
  85 a domain error occurs,
  86 and a NaN is returned.
  87
  88 If the correct result would overflow,
  89 a range error occurs,
  90 and the functions return
  91 .BR HUGE_VAL ,
  92 .BR HUGE_VALF ,
  93 or
  94 .BR HUGE_VALL ,
  95 respectively, with the mathematically correct sign.
  96 .\" I think overflow can't occur, because the closest floating-point
  97 .\" representation of pi/2 is still not close enough to pi/2 to
  98 .\" produce a large enough value to overflow.
  99 .\" Testing certainly seems to bear this out.  -- mtk, Jul 08
 100 .\"
 101 .\" POSIX.1 allows an optional underflow error;
 102 .\" glibc 2.8 doesn't do this
 103 .\" POSIX.1 an optional range error for subnormal x;
 104 .\" glibc 2.8 doesn't do this
 105 .SH ERRORS
 106 See
 107 .BR math_error (7)
 108 for information on how to determine whether an error has occurred
 109 when calling these functions.
 110 .PP
 111 The following errors can occur:
 112 .TP
 113 Domain error: \fIx\fP is an infinity
 114 .I errno
 115 is set to
 116 .BR EDOM
 117 (but see BUGS).
 118 An invalid floating-point exception
 119 .RB ( FE_INVALID )
 120 is raised.
 121 .TP
 122 Range error: result overflow
 123 .\" Unable to test this case, since the best approximation of
 124 .\" pi/2 in double precision only yields a tan() value of 1.633e16.
 125 .\" .I errno
 126 .\" is set to
 127 .\" .BR ERANGE .
 128 An overflow floating-point exception
 129 .RB ( FE_OVERFLOW )
 130 is raised.
 131 .SH ATTRIBUTES
 132 For an explanation of the terms used in this section, see
 133 .BR attributes (7).
 134 .TS
 135 allbox;
 136 lbw21 lb lb
 137 l l l.
 138 Interface       Attribute       Value
 139 T{
 140 .BR tan (),
 141 .BR tanf (),
 142 .BR tanl ()
 143 T}      Thread safety   MT-Safe
 144 .TE
 145 .SH CONFORMING TO
 146 C99, POSIX.1-2001, POSIX.1-2008.
 147
 148 The variant returning
 149 .I double
 150 also conforms to
 151 SVr4, 4.3BSD, C89.
 152 .SH BUGS
 153 Before version 2.10, the glibc implementation did not set
 154 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=6782
 155 .I errno
 156 to
 157 .B EDOM
 158 when a domain error occurred.
 159 .SH SEE ALSO
 160 .BR acos (3),
 161 .BR asin (3),
 162 .BR atan (3),
 163 .BR atan2 (3),
 164 .BR cos (3),
 165 .BR ctan (3),
 166 .BR sin (3)