double jacobi_cn ( double u, double m );
double jacobi_dn ( double u, double m );
double jacobi_sn ( double u, double m );
void sncndn ( double u, double m, double &sn, double &cn, double &dn );
void jacobi_cn_values ( int &n_data, double &u, double &a, double &k, 
  double &m, double &fx );
void jacobi_dn_values ( int &n_data, double &u, double &a, double &k, 
  double &m, double &fx );
void jacobi_sn_values ( int &n_data, double &u, double &a, double &k, 
  double &m, double &fx );