1ACOS(3P) POSIX Programmer's Manual ACOS(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 acos, acosf, acosl — arc cosine functions
14
16 #include <math.h>
17 double acos(double x);
19 float acosf(float x);
20 long double acosl(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 principal value of the arc cosine of
29 their argument x. The value of x should be in the range [−1,1].
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 arc cosine
39 of x, in the range [0,π] radians.
40 For finite values of x not in the range [−1,1], a domain error shall
42 occur, and either a NaN (if supported), or an implementation-defined
43 value shall be returned.
44 If x is NaN, a NaN shall be returned.
46 If x is +1, +0 shall be returned.
48 If x is ±Inf, a domain error shall occur, and a NaN shall be returned.
50
52 These functions shall fail if:
53 Domain Error
55 The x argument is finite and is not in the range [−1,1], or
56 is ±Inf.
57 If the integer expression (math_errhandling & MATH_ERRNO)
59 is non-zero, then errno shall be set to [EDOM]. If the
60 integer expression (math_errhandling & MATH_ERREXCEPT) is
61 non-zero, then the invalid floating-point exception shall
62 be raised.
63 The following sections are informative.
65
67 None.
68
70 On error, the expressions (math_errhandling & MATH_ERRNO) and
71 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
72 at least one of them must be non-zero.
73
75 None.
76
78 None.
79
81 cos(), feclearexcept(), fetestexcept(), isnan()
82 The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
84 Error Conditions for Mathematical Functions, <math.h>
85
87 Portions of this text are reprinted and reproduced in electronic form
88 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
89 -- Portable Operating System Interface (POSIX), The Open Group Base
90 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
91 cal and Electronics Engineers, Inc and The Open Group. (This is
92 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
93 event of any discrepancy between this version and the original IEEE and
94 The Open Group Standard, the original IEEE and The Open Group Standard
95 is the referee document. The original Standard can be obtained online
96 at http://www.unix.org/online.html .
97 Any typographical or formatting errors that appear in this page are
99 most likely to have been introduced during the conversion of the source
100 files to man page format. To report such errors, see https://www.ker‐
101 nel.org/doc/man-pages/reporting_bugs.html .
102IEEE/The Open Group 2013 ACOS(3P)