asinh
    (PHP 4 >= 4.1.0, PHP 5)
asinh -- Inverse hyperbolic sine
Description
float 
asinh ( float arg)
     Returns the inverse hyperbolic sine of
     arg, i.e. the value whose
     hyperbolic sine is arg.
    
Note: This function is not
implemented on Windows platforms.
     See also:
     asin(),
     acosh(), and
     atanh().