#define MILD_ANGLE  32

{

  double pi = TMath::Pi();

  TH1F* h = new TH1F("h","h",90,0,90); 

  double at = tan(MILD_ANGLE*pi/180.);

  double Fp[2] = {1,0};
  double Fx[2] = {0,at};
  double X[2];

cout << "Fp : " << Fp[0] << " Fx : " << Fx[1] << endl;

  for (int i=0;i<100000;i++) {
    double Hp=gRandom->Uniform(-1,1);
    double Hx=gRandom->Uniform(-1,1);

    X[0] = Fp[0]*Hp+Fx[0]*Hx;
    X[1] = Fp[1]*Hp+Fx[1]*Hx;

    double angle = fabs(atan2(X[1],X[0])*180./pi);
    
    h->Fill(angle);
  }

  h->Draw();

}
