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
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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 2008-08-05 ""  "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 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
  58 .I cc\ -std=c99
  59 .ad b
  60 .SH DESCRIPTION
  61 The
  62 .BR tan ()
  63 function returns the tangent of \fIx\fP, where \fIx\fP is
  64 given in radians.
  65 .SH RETURN VALUE
  66 On success, these functions return the tangent of
  67 .IR x .
  68
  69 If
  70 .I x
  71 is a NaN, a NaN is returned.
  72
  73 If
  74 .I x
  75 is positive infinity or negative infinity,
  76 a "domain error" occurs,
  77 and a NaN is returned.
  78
  79 If the correct result would overflow,
  80 a "range error" occurs,
  81 and the functions return
  82 .BR HUGE_VAL ,
  83 .BR HUGE_VALF ,
  84 or
  85 .BR HUGE_VALL ,
  86 respectively, with the mathematically correct sign.
  87 .\" I think overflow can't occur, because the closest floating-point
  88 .\" representation of pi/2 is still not close enough to pi/2 to
  89 .\" produce a large enough value to overflow.
  90 .\" Testing certainly seems to bear this out.  -- mtk, Jul 08
  91 .\"
  92 .\" POSIX.1 allows an optional underflow error;
  93 .\" glibc 2.8 doesn't do this
  94 .\" POSIX.1 an optional range error for subnormal x;
  95 .\" glibc 2.8 doesn't do this
  96 .SH ERRORS
  97 See
  98 .BR math_error (7)
  99 for information on how to determine whether an error has occurred
 100 when calling these functions.
 101 .PP
 102 The following errors can occur:
 103 .TP
 104 Domain error: \fIx\fP is an infinity
 105 .\" .I errno
 106 .\" is set to
 107 .\" .BR EDOM .
 108 An invalid floating-point exception
 109 .RB ( FE_INVALID )
 110 is raised.
 111 .TP
 112 Range error: result overflow
 113 .\" Unable to test this case, since the best approximation of
 114 .\" pi/2 in double precision only yields a tan() value of 1.633e16.
 115 .\" .I errno
 116 .\" is set to
 117 .\" .BR ERANGE .
 118 An overflow floating-point exception
 119 .RB ( FE_OVERFLOW )
 120 is raised.
 121 .PP
 122 These functions do not set
 123 .IR errno .
 124 .\" FIXME . Is it intentional that these functions do not set
 125 .\" errno (at least for domain error)?
 126 .\" Bug raised: http://sourceware.org/bugzilla/show_bug.cgi?id=6782
 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 "SEE ALSO"
 134 .BR acos (3),
 135 .BR asin (3),
 136 .BR atan (3),
 137 .BR atan2 (3),
 138 .BR cos (3),
 139 .BR ctan (3),
 140 .BR sin (3)