acos(3M)
NAME
acos − arc cosine function
SYNOPSIS
cc [ flag ... ] file ... −lm [ library ... ]
#include <math.h>
double acos(double x);
DESCRIPTION
The acos() function computes the principal value of the arc cosine of x. The value of x should be in the range [−1,1].
RETURN VALUES
Upon successful completion, acos() returns the arc cosine of x, in the range [0, π] radians. If the value of x is not in the range [−1,1], and is not ±Inf or NaN, either 0.0 or NaN is returned and errno is set to EDOM.
If x is NaN, NaN is returned. If x is ±Inf, either 0.0 is returned and errno is set to EDOM, or NaN is returned and errno may be set to EDOM.
For exceptional cases, matherr(3M) tabulates the values to be returned as dictated by Standards other than XPG4.
ERRORS
The acos() function will fail if:
EDOM The value x is not ±Inf or NaN and is not in the range [−1,1].
The acos() function may fail if:
EDOM The value x is ±Inf.
USAGE
An application wishing to check for error situations should set errno to 0 before calling acos(). If errno is non-zero on return, or the value NaN is returned, an error has occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
SEE ALSO
cos(3M), isnan(3M), matherr(3M), attributes(5), standards(5)
SunOS 5.6 — Last change: 29 Dec 1996