These functions calculate the complex arc hyperbolic sine of
z. If y = casinh(z), then
z = csinh(y). The imaginary part of y is chosen
in the interval [-pi/2,pi/2].
One has:
casinh(z) = clog(z + csqrt(z * z + 1))
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).