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()