Name

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    ASINH

Purpose

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    Return the inverse hyperbolic sine of the argument

Explanation

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    The inverse hyperbolic sine is used for the calculation of asinh
    magnitudes, see Lupton et al. (1999, AJ, 118, 1406)

Calling Sequence

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    result = asinh( x)

Inputs

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    X - hyperbolic sine, numeric scalar or vector or multidimensional array
        (not complex)

Output

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    result - inverse hyperbolic sine, same number of elements as X
              double precision if X is double, otherwise floating pt.

Method

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    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).

Revision History

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    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