The acosh(), asinh() and atanh() functions compute the inverse hyperbolic cosine, sine, and tangent of their argument, respectively.

The acosh(), asinh() and atanh() functions return the inverse hyperbolic cosine, sine, and tangent of their argument, respectively.

The acosh() function returns NaN and sets errno to EDOM when its argument is less than 1.0.

The atanh() function returns NaN and sets errno to EDOM when its argument has absolute value greater than 1.0.

The atanh() function returns +-Inf and sets errno to ERANGE when its argument is +-1.0.

If x is NaN, the asinh(), acosh() and atanh() functions return NaN.

For exceptional cases, matherr(3M) tabulates the values to be returned as dictated by Standards other than XPG4.

The acosh() function will fail if:

EDOM

The x argument is less than 1.0.

The atanh() function will fail if:

EDOM

The x argument has an absolute value greater than 1.0.

ERANGE

The x argument has an absolute value equal to 1.0

See attributes(5) for descriptions of the following attributes:

cosh(3M), matherr(3M), sinh(3M), tanh(3M), attributes(5), standards(5)