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
12 tan, tanf, tanl — tangent function
13
15 #include <math.h>
16 double tan(double x);
18 float tanf(float x);
19 long double tanl(long double x);
20
22 The functionality described on this reference page is aligned with the
23 ISO C standard. Any conflict between the requirements described here
24 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
25 defers to the ISO C standard.
26 These functions shall compute the tangent of their argument x, measured
28 in radians.
29 An application wishing to check for error situations should set errno
31 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
32 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
33 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
34 occurred.
35
37 Upon successful completion, these functions shall return the tangent of
38 x.
39 If the correct value would cause underflow, and is not representable, a
41 range error may occur, and tan(), tanf(), and tanl() shall return 0.0,
42 or (if IEC 60559 Floating-Point is not supported) an implementation-
43 defined value no greater in magnitude than DBL_MIN, FLT_MIN, and
44 LDBL_MIN, respectively.
45 If x is NaN, a NaN shall be returned.
47 If x is ±0, x shall be returned.
49 If x is subnormal, a range error may occur
51 and x should be returned.
52 If x is not returned, tan(), tanf(), and tanl() shall return an imple‐
54 mentation-defined value no greater in magnitude than DBL_MIN, FLT_MIN,
55 and LDBL_MIN, respectively.
56 If x is ±Inf, a domain error shall occur, and either a NaN (if sup‐
58 ported), or an implementation-defined value shall be returned.
59 If the correct value would cause underflow, and is representable, a
61 range error may occur and the correct value shall be returned.
62 If the correct value would cause overflow, a range error shall occur
64 and tan(), tanf(), and tanl() shall return ±HUGE_VAL, ±HUGE_VALF, and
65 ±HUGE_VALL, respectively, with the same sign as the correct value of
66 the function.
67
69 These functions shall fail if:
70 Domain Error
72 The value of x is ±Inf.
73 If the integer expression (math_errhandling & MATH_ERRNO)
75 is non-zero, then errno shall be set to [EDOM]. If the
76 integer expression (math_errhandling & MATH_ERREXCEPT) is
77 non-zero, then the invalid floating-point exception shall
78 be raised.
79 Range Error The result overflows
81 If the integer expression (math_errhandling & MATH_ERRNO)
83 is non-zero, then errno shall be set to [ERANGE]. If the
84 integer expression (math_errhandling & MATH_ERREXCEPT) is
85 non-zero, then the overflow floating-point exception shall
86 be raised.
87 These functions may fail if:
89 Range Error The result underflows, or the value of x is subnormal.
91 If the integer expression (math_errhandling & MATH_ERRNO)
93 is non-zero, then errno shall be set to [ERANGE]. If the
94 integer expression (math_errhandling & MATH_ERREXCEPT) is
95 non-zero, then the underflow floating-point exception shall
96 be raised.
97 The following sections are informative.
99
101 Taking the Tangent of a 45-Degree Angle
102 #include <math.h>
103 ...
104 double radians = 45.0 * M_PI / 180;
105 double result;
106 ...
107 result = tan (radians);
108
110 There are no known floating-point representations such that for a nor‐
111 mal argument, tan(x) is either overflow or underflow.
112 These functions may lose accuracy when their argument is near a multi‐
114 ple of π/2 or is far from 0.0.
115 On error, the expressions (math_errhandling & MATH_ERRNO) and
117 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
118 at least one of them must be non-zero.
119
121 None.
122
124 None.
125
127 atan(), feclearexcept(), fetestexcept(), isnan()
128 The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
130 Error Conditions for Mathematical Functions, <math.h>
131
133 Portions of this text are reprinted and reproduced in electronic form
134 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
135 table Operating System Interface (POSIX), The Open Group Base Specifi‐
136 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
137 Electrical and Electronics Engineers, Inc and The Open Group. In the
138 event of any discrepancy between this version and the original IEEE and
139 The Open Group Standard, the original IEEE and The Open Group Standard
140 is the referee document. The original Standard can be obtained online
141 at http://www.opengroup.org/unix/online.html .
142 Any typographical or formatting errors that appear in this page are
144 most likely to have been introduced during the conversion of the source
145 files to man page format. To report such errors, see https://www.ker‐
146 nel.org/doc/man-pages/reporting_bugs.html .
147IEEE/The Open Group 2017 TAN(3P)