1TAN(3P) POSIX Programmer's Manual TAN(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 tan, tanf, tanl — tangent function
14
16 #include <math.h>
17 double tan(double x);
19 float tanf(float x);
20 long double tanl(long double x);
21
23 The functionality described on this reference page is aligned with the
24 ISO C standard. Any conflict between the requirements described here
25 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
26 defers to the ISO C standard.
27 These functions shall compute the tangent of their argument x, measured
29 in radians.
30 An application wishing to check for error situations should set errno
32 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
33 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
34 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
35 occurred.
36
38 Upon successful completion, these functions shall return the tangent of
39 x.
40 If the correct value would cause underflow, and is not representable, a
42 range error may occur, and tan(), tanf(), and tanl() shall return 0.0,
43 or (if IEC 60559 Floating-Point is not supported) an implementation-
44 defined value no greater in magnitude than DBL_MIN, FLT_MIN, and
45 LDBL_MIN, respectively.
46 If x is NaN, a NaN shall be returned.
48 If x is ±0, x shall be returned.
50 If x is subnormal, a range error may occur
52 and x should be returned.
53 If x is not returned, tan(), tanf(), and tanl() shall return an imple‐
55 mentation-defined value no greater in magnitude than DBL_MIN, FLT_MIN,
56 and LDBL_MIN, respectively.
57 If x is ±Inf, a domain error shall occur, and either a NaN (if sup‐
59 ported), or an implementation-defined value shall be returned.
60 If the correct value would cause underflow, and is representable, a
62 range error may occur and the correct value shall be returned.
63 If the correct value would cause overflow, a range error shall occur
65 and tan(), tanf(), and tanl() shall return ±HUGE_VAL, ±HUGE_VALF, and
66 ±HUGE_VALL, respectively, with the same sign as the correct value of
67 the function.
68
70 These functions shall fail if:
71 Domain Error
73 The value of x is ±Inf.
74 If the integer expression (math_errhandling & MATH_ERRNO)
76 is non-zero, then errno shall be set to [EDOM]. If the
77 integer expression (math_errhandling & MATH_ERREXCEPT) is
78 non-zero, then the invalid floating-point exception shall
79 be raised.
80 Range Error The result overflows
82 If the integer expression (math_errhandling & MATH_ERRNO)
84 is non-zero, then errno shall be set to [ERANGE]. If the
85 integer expression (math_errhandling & MATH_ERREXCEPT) is
86 non-zero, then the overflow floating-point exception shall
87 be raised.
88 These functions may fail if:
90 Range Error The result underflows, or the value of x is subnormal.
92 If the integer expression (math_errhandling & MATH_ERRNO)
94 is non-zero, then errno shall be set to [ERANGE]. If the
95 integer expression (math_errhandling & MATH_ERREXCEPT) is
96 non-zero, then the underflow floating-point exception shall
97 be raised.
98 The following sections are informative.
100
102 Taking the Tangent of a 45-Degree Angle
103 #include <math.h>
104 ...
105 double radians = 45.0 * M_PI / 180;
106 double result;
107 ...
108 result = tan (radians);
109
111 There are no known floating-point representations such that for a nor‐
112 mal argument, tan(x) is either overflow or underflow.
113 These functions may lose accuracy when their argument is near a multi‐
115 ple of π/2 or is far from 0.0.
116 On error, the expressions (math_errhandling & MATH_ERRNO) and
118 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
119 at least one of them must be non-zero.
120
122 None.
123
125 None.
126
128 atan(), feclearexcept(), fetestexcept(), isnan()
129 The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
131 Error Conditions for Mathematical Functions, <math.h>
132
134 Portions of this text are reprinted and reproduced in electronic form
135 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
136 -- Portable Operating System Interface (POSIX), The Open Group Base
137 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
138 cal and Electronics Engineers, Inc and The Open Group. (This is
139 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
140 event of any discrepancy between this version and the original IEEE and
141 The Open Group Standard, the original IEEE and The Open Group Standard
142 is the referee document. The original Standard can be obtained online
143 at http://www.unix.org/online.html .
144 Any typographical or formatting errors that appear in this page are
146 most likely to have been introduced during the conversion of the source
147 files to man page format. To report such errors, see https://www.ker‐
148 nel.org/doc/man-pages/reporting_bugs.html .
149IEEE/The Open Group 2013 TAN(3P)