acos, acosf, acosl - arc cosine function
#include <math.h>
double acos(double x);
float acosf(float x);
long double acosl(long double x);
Link with
-lm.
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 versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions calculate the arc cosine of
x; that is the value whose
cosine is
x.
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.
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: x is outside the range [-1, 1]
- errno is set to EDOM. An invalid floating-point exception
(FE_INVALID) is raised.
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| acos (), acosf (), acosl () |
Thread safety |
MT-Safe |
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double also conforms to SVr4, 4.3BSD, C89.
asin(3),
atan(3),
atan2(3),
cacos(3),
cos(3),
sin(3),
tan(3)