Double_t fff(Double_t *x,Double_t *p)
{
double E=p[0];double theta=x[0]/180*TMath::Pi();

double Ep=E/(1+E/(511)*(1-cos(theta)));
	double u=pow(sin(theta),2)/(E/Ep+Ep/E-pow(sin(theta),2));
return u;

}

Double_t ff(Double_t *x,Double_t *p)
{ 
	double E=p[0];double theta=x[0]/180*TMath::Pi();

	double Ep=E/(1+E/(511)*(1-cos(theta)));
//	double s=6.652e-29;
	//double c=3*s/(16*TMath::Pi())*pow(Ep/E,2)*(E/Ep+Ep/E-2*pow(sin(theta),2));
	double c=pow(Ep/E,2)*((E/Ep+Ep/E)-pow(sin(theta),2))/2;
	return c;

}

void huatu()
{
	TCanvas *c1=new TCanvas("c1","c1",800,600);
	c1->cd();
	gRandom->SetSeed(0);
	TF1*f1 = new TF1("f1",ff,0,360,1);
	f1->SetParameter(0,50);
	const int N=360;
	double xx[N]={0};
	double yy[N]={0};
	double rr;
	for(int i=0;i<N;i++){
		rr=f1->Eval(i);
		xx[i]=i;
		yy[i]=rr;
	}
	TGraphPolar *gr = new TGraphPolar(N, xx, yy);
	gr->SetMarkerStyle(21);
	gr->SetMarkerColor(kBlue);
	gr->SetFillColor(kBlue);
	gr->SetMinimum(0); 
	gr->SetMaximum(1); 
	gr->GetYaxis()->SetRange(0,1); 
	gr->Draw("AP");
	//f1->Draw();


}