#include <math.h>

double * oscillatore(double *x, double t) { // oscillatore armonico
  double *derivata=new double[2];
  double f=1.; // frequenza=1 Hz;
  double omega=2.*M_PI*f; 
  derivata[0]=x[1];                // dx/dt = v;
  derivata[1]=-omega*omega*x[0];   // dv/dt = -omega^2 x
  return derivata;
}