Return the inverse hyperbolic sine of the argument
The inverse hyperbolic sine is used for the calculation of asinh
magnitudes, see Lupton et al. (1999, AJ, 118, 1406)
result = asinh( x)
X - hyperbolic sine, numeric scalar or vector or multidimensional array
result - inverse hyperbolic sine, same number of elements as X
double precision if X is double, otherwise floating pt.
Expression given in Numerical Recipes, Press et al. (1992), eq. 5.6.7
Note that asinh(-x) = -asinh(x) and that asinh(0) = 0. and that
if y = asinh(x) then x = sinh(y).
Written W. Landsman February, 2001
Work for multi-dimensional arrays W. Landsman August 2002
Simplify coding, and work for scalars again W. Landsman October 2003