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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15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
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27 .\" References consulted:
28 .\" Linux libc source code
29 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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)
35 .TH TAN 3 2010-09-11 "" "Linux Programmer's Manual"
37 tan, tanf, tanl \- tangent function
42 .BI "double tan(double " x );
44 .BI "float tanf(float " x );
46 .BI "long double tanl(long double " x );
52 Feature Test Macro Requirements for glibc (see
53 .BR feature_test_macros (7)):
60 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
61 _POSIX_C_SOURCE\ >=\ 200112L;
70 function returns the tangent of
77 On success, these functions return the tangent of
82 is a NaN, a NaN is returned.
86 is positive infinity or negative infinity,
87 a domain error occurs,
88 and a NaN is returned.
90 If the correct result would overflow,
92 and the functions return
97 respectively, with the mathematically correct sign.
98 .\" I think overflow can't occur, because the closest floating-point
99 .\" representation of pi/2 is still not close enough to pi/2 to
100 .\" produce a large enough value to overflow.
101 .\" Testing certainly seems to bear this out. -- mtk, Jul 08
103 .\" POSIX.1 allows an optional underflow error;
104 .\" glibc 2.8 doesn't do this
105 .\" POSIX.1 an optional range error for subnormal x;
106 .\" glibc 2.8 doesn't do this
110 for information on how to determine whether an error has occurred
111 when calling these functions.
113 The following errors can occur:
115 Domain error: \fIx\fP is an infinity
120 An invalid floating-point exception
124 Range error: result overflow
125 .\" Unable to test this case, since the best approximation of
126 .\" pi/2 in double precision only yields a tan() value of 1.633e16.
130 An overflow floating-point exception
135 The variant returning
140 Before version 2.10, the glibc implementation did not set
141 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=6782
145 when a domain error occurred.