1ACOS(P)                    POSIX Programmer's Manual                   ACOS(P)
2
3
4

NAME

6       acos, acosf, acosl - arc cosine functions
7

SYNOPSIS

9       #include <math.h>
10
11       double acos(double x);
12       float acosf(float x);
13       long double acosl(long double x);
14
15

DESCRIPTION

17       These  functions shall compute the principal value of the arc cosine of
18       their argument x. The value of x should be in the range [-1,1].
19
20       An application wishing to check for error situations should  set  errno
21       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
22       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
23       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
24       occurred.
25

RETURN VALUE

27       Upon successful completion, these functions shall return the arc cosine
28       of x, in the range [0,pi] radians.
29
30       For  finite  values  of x not in the range [-1,1], a domain error shall
31       occur, and    either a NaN  (if  supported),  or    an  implementation-
32       defined value shall be returned.
33
34       If x is NaN, a NaN shall be returned.
35
36       If x is +1, +0 shall be returned.
37
38       If  x  is  ±Inf,  a domain error shall occur, and either a NaN (if sup‐
39       ported), or an implementation-defined value shall be returned.
40

ERRORS

42       These functions shall fail if:
43
44       Domain Error
45              The x argument is finite and is not in the range  [-1,1],     or
46              is ±Inf.
47
48       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
49       then  errno  shall  be  set  to  [EDOM].  If  the  integer   expression
50       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then  the invalid
51       floating-point exception shall be raised.
52
53
54       The following sections are informative.
55

EXAMPLES

57       None.
58

APPLICATION USAGE

60       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
61       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
62       at least one of them must be non-zero.
63

RATIONALE

65       None.
66

FUTURE DIRECTIONS

68       None.
69

SEE ALSO

71       cos() , feclearexcept() , fetestexcept() , isnan() , the  Base  Defini‐
72       tions  volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
73       Conditions for Mathematical Functions, <math.h>
74

76       Portions of this text are reprinted and reproduced in  electronic  form
77       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
78       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
79       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
80       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
81       event of any discrepancy between this version and the original IEEE and
82       The Open Group Standard, the original IEEE and The Open Group  Standard
83       is  the  referee document. The original Standard can be obtained online
84       at http://www.opengroup.org/unix/online.html .
85
86
87
88IEEE/The Open Group                  2003                              ACOS(P)
Impressum