{
 TF1  *f1 = new TF1("f1","gaus(x)",0,10);
 TF1  *f2 = new TF1("f2","10.-x",0,10);
 f2->SetParameter(0,1);
 f2->Draw();
 f1->SetParameter(0,2);
 f1->SetParameter(1,4);
 f1->SetParameter(2,2.5);
 f1->Draw();
 TF1  *f3 = new TF1("f3","f1+f2",0,10);
 f3->Draw();
 f3->SetParameter(0,3);
 f3->SetParameter(2,0.5);
 f3->Draw();
 f2->Draw("same");
 f1->SetParameter(0,3);
 f1->SetParameter(2,0.5);
 f1->Draw("same");

 TH1F* h = new TH1F("h","h",100,0,0); //auto range
 for (int i=0;i<10000;i++) {
   h->Fill(f3->GetRandom());
 }
 h->Draw();
 TF1* f4 = new TF1("f4","[0]*TMath::Exp( -0.5* ((x-[1])/[2])*((x-[1])/[2]))+[3]-[4]*x",0,10);
 f4->SetParameter(2,4);
 TFitResultPtr r = h->Fit(f4,"S");
 r->Print("V");
 
}