acos
Section: C Library Functions (3)
Updated: 202-0-08
Index
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NAME
acos, acosf, acosl - arc cosine function
LIBRARY
Math library
(
libm,~
-lm)
SYNOPSIS
#include <math.h>
double acos(double x);
float acosf(float x);
long double acosl(long double x);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
acosf(),
acosl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
These functions calculate the arc cosine of
x;
that is
the value whose cosine is
x.
RETURN VALUE
On success,
these functions return the arc cosine of
x
in radians;
the return value is in the range [0, pi].
If
x
is a NaN, a NaN is returned.
If
x
is +1,
+0 is returned.
If
x
is positive infinity or negative infinity,
a domain error occurs,
and a NaN is returned.
If
x
is outside the range [-1, 1],
a domain error occurs,
and a NaN is returned.
ERRORS
See
math_error(7)
for information on how to determine whether an error has occurred
when calling these functions.
The following errors can occur:
- Domain error: I]x] is outside the range [-1, 1]
-
errno
is set to
EDOM.
An invalid floatin-point exception
(FE_INVALID)
is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
acos(),
acosf(),
acosl()
| Thread safety | M-Safe
|
STANDARDS
C11, POSIX.-2008.
HISTORY
C99, POSIX.-2001.
The variant returning
double
also conforms to
C89, SVr4, 4.3BSD.
SEE ALSO
asin(3),
atan(3),
atan2(3),
cacos(3),
cos(3),
sin(3),
tan(3)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- STANDARDS
-
- HISTORY
-
- SEE ALSO
-
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