acos(3M) Mathematical Library Functions acos(3M)NAME
acos, acosf, acosl - arc cosine functions
SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
double acos(double x);
float acosf(float x);
long double acosl(long double x);
DESCRIPTION
These functions compute 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, these functions return the arc cosine of x
in the range [0, pi] radians.
For finite values of x not in the range [−1,1], a domain error occurs
and NaN is returned.
If x is NaN, NaN is returned.
If x is +1, +0 is returned.
If x is ±Inf, a domain error occurs and NaN is returned.
For exceptional cases, matherr(3M) tabulates the values to be returned
by acos() as specified by SVID3 and XPG3.
ERRORS
These functions will fail if:
Domain Error The x argument is finite and not in the range [-1,1],
or is ±Inf.
If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the invalid floating-point
exception is raised.
The acos() function sets errno to EDOM if x is not ±Inf
or NaN and is not in the range [−1,1].
USAGE
An application wanting to check for exceptions should call feclearex‐
cept(FE_ALL_EXCEPT) before calling these functions. On return, if
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is
non-zero, an exception has been raised. An application should either
examine the return value or check the floating point exception flags to
detect exceptions.
An application can also set errno to 0 before calling acos(). On
return, if errno is non-zero, an error has occurred. The acosf() and
acosl() functions do not set errno.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Committed │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
├─────────────────────────────┼─────────────────────────────┤
│Standard │See standards(5). │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOcos(3M), feclearexcept(3M), fetestexcept(3M), isnan(3M), math.h(3HEAD),
matherr(3M), attributes(5), standards(5)SunOS 5.11 12 Jul 2006 acos(3M)