Computes the inverse cosine of a given value.
#include <math.h>
float acosf (x)
float x;
long double acosl (x)
long double x;
double acos (x)
double x;
_Decimal32 acosd32 (x)
_Decimal32 x;
_Decimal64 acosd64 (x)
_Decimal64 x;
_Decimal128 acosd128 (x)
_Decimal128 x;The acosf, acosl, acos, acosd32, acosd64, and acosd128 subroutines compute the principal value of the arc cosine of the x parameter. The value of x should be in the range [-1,1].
An application wishing to check for error situations should set the errno global variable to zero and call fetestexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is nonzero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error has occurred.
| Item | Description |
|---|---|
| x | Specifies the value to be computed. |
Upon successful completion, these subroutines 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 a NaN is returned.
If x is NaN, a NaN is returned.
If x is +1, 0 is returned.
If x is ±Inf, a domain error occurs, and a NaN is returned.