double asinh(double x);
asinh calculates the hyperbolic sine of x.
If |x| > ~709.782, errno is set to EDOM and asinh returns HUGE_VAL.
If x is +∞, −∞, or NaN, asinh returns |x|. If |x| > ~709.782, asinh returns +∞ or −∞ depending upon the sign of x.