cpp/numeric/math/cosh

@1-3@ Computes the hyperbolic cosine of.

Return value
If no errors occur, the hyperbolic cosine of ($cosh(num)$, or $$) is returned.

If a range error due to overflow occurs, huge_val,, or is returned.

Error handling
Errors are reported as specified in math_errhandling.

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