cpp/numeric/math/acosh

@1-3@ Computes the inverse hyperbolic cosine of. @A@ Additional overloads are provided for all integer types, which are treated as.

Return value
If no errors occur, the inverse hyperbolic cosine of ($cosh-1 (num)$, or $arcosh(num)$) on the interval $[0, +∞]$, is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

Error handling
Errors are reported as specified in math_errhandling.

If the argument is less than 1, a domain error occurs.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),
 * if the argument is less than 1, fe_invalid is raised an NaN is returned
 * if the argument is 1, +0 is returned
 * if the argument is +∞, +∞ is returned
 * if the argument is NaN, NaN is returned