acos3
Arc cosine function
Usage
#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
Library
Math library (libm, -lm)
Overview
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 |
Releases
19 releases since Debian 1.1 (Buzz); the text changed 13 times.