public static double evaluate(double u, double m)
//****************************************************************************80
//
// Purpose:
//
// JACOBI_DN evaluates the Jacobi elliptic function DN(U,M).
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 26 June 2018
//
// Author:
//
// Original ALGOL version by Roland Bulirsch.
// C++ version by John Burkardt
//
// Reference:
//
// Roland Bulirsch,
// Numerical calculation of elliptic integrals and elliptic functions,
// Numerische Mathematik,
// Volume 7, Number 1, 1965, pages 78-90.
//
// Parameters:
//
// Input, double U, M, the arguments.
//
// Output, double JACOBI_DN, the function value.
//
{
double cn = 0;
double dn = 0;
double sn = 0;
Jacobi.sncndn(u, m, ref sn, ref cn, ref dn);
return(dn);
}