Computes the inverse hyperbolic cosine.
#include <math.h> float acoshf (x) float x; long double acoshl (X) long double x; double acosh (x) double x;
The acoshf, or acoshl subroutine computes the inverse hyperbolic cosine of the x parameter.
The acosh subroutine returns the hyperbolic arc cosine specified by the x parameter, in the range 1 to the +HUGE_VAL value.
An application wishing to check for error situations should set errno to zero and call fetestexcept(FE_ALL_EXCEPT) before calling these subroutines. Upon return, if the errno global variable is nonzero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error has occurred.
| x | Specifies the value to be computed. |
Upon successful completion, the acoshf, or acoshl subroutine returns the inverse hyperbolic cosine of the given argument.
For finite values of x < 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, +Inf is returned.
If x is -Inf, a domain error occurs, and a NaN is returned.
The acosh subroutine returns NaNQ (not-a-number) and sets errno to EDOM if the x parameter is less than the value of 1.
math.h in AIX 5L Version 5.2 Files Reference.