acosf (3) Linux Manual Page
acos, acosf, acosl – arc cosine function
Synopsis
#include <math.h>Link with -lm.
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 versions <= 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: x is outside the range [-1, 1]
- errno is set to EDOM. An invalid floating-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 | MT-Safe |
Conforming To
C99, POSIX.1-2001, POSIX.1-2008. The variant returning double also conforms to SVr4, 4.3BSD, C89.