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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  14 .\" Since the Linux kernel and libraries are constantly changing, this
  15 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
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  22 .\" Formatted or processed versions of this manual, if unaccompanied by
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  24 .\"
  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  30 .\" Modified 2002-07-27 by Walter Harms
  31 .\"     (walter.harms@informatik.uni-oldenburg.de)
  32 .\"
  33 .TH TAN 3 2010-09-11 ""  "Linux Programmer's Manual"
  34 .SH NAME
  35 tan, tanf, tanl \- tangent function
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <math.h>
  39 .sp
  40 .BI "double tan(double " x );
  41 .br
  42 .BI "float tanf(float " x );
  43 .br
  44 .BI "long double tanl(long double " x );
  45 .fi
  46 .sp
  47 Link with \fI\-lm\fP.
  48 .sp
  49 .in -4n
  50 Feature Test Macro Requirements for glibc (see
  51 .BR feature_test_macros (7)):
  52 .in
  53 .sp
  54 .ad l
  55 .BR tanf (),
  56 .BR tanl ():
  57 .RS 4
  58 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
  59 _POSIX_C_SOURCE\ >=\ 200112L;
  60 .br
  61 or
  62 .I cc\ -std=c99
  63 .RE
  64 .ad
  65 .SH DESCRIPTION
  66 The
  67 .BR tan ()
  68 function returns the tangent of \fIx\fP, where \fIx\fP is
  69 given in radians.
  70 .SH RETURN VALUE
  71 On success, these functions return the tangent of
  72 .IR x .
  73
  74 If
  75 .I x
  76 is a NaN, a NaN is returned.
  77
  78 If
  79 .I x
  80 is positive infinity or negative infinity,
  81 a domain error occurs,
  82 and a NaN is returned.
  83
  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 "CONFORMING TO"
 128 C99, POSIX.1-2001.
 129 The variant returning
 130 .I double
 131 also conforms to
 132 SVr4, 4.3BSD, C89.
 133 .SH BUGS
 134 Before version 2.10, the glibc implementation did not set
 135 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=6782
 136 .I errno
 137 to
 138 .B EDOM
 139 when a domain error occurred.
 140 .SH "SEE ALSO"
 141 .BR acos (3),
 142 .BR asin (3),
 143 .BR atan (3),
 144 .BR atan2 (3),
 145 .BR cos (3),
 146 .BR ctan (3),
 147 .BR sin (3)