NAME
        IEEEDPTanh -- compute the hyperbolic tangent of a floating point number

   SYNOPSIS
          x   = IEEEDPTanh(  y  );
        d0/d1              d0/d1

        double  x,y;

   FUNCTION
        Compute hyperbolic tangent of y in IEEE double precision

   INPUTS
        y - IEEE double precision floating point value

   RESULT
        x - IEEE double precision floating point value

   BUGS

   SEE ALSO
        ieeedpsinh(), ieeedpcosh()