#include "TCanvas.h"
#include "TF1.h"
#include "TMath.h"

Double_t BetaFunc(Double_t *x, Double_t *p);


void functest()
{
  new TCanvas("func1","func1");
  TF1* func1 = new TF1("func1",
             "TMath::BetaIncomplete(.5, x, 11-x )",
             0.,10.);
  func1->Draw();

  new TCanvas("func2","func2");
  TF1* func2 = new TF1("func2",&BetaFunc,0.,10.,0);
  func2->Draw();
}

Double_t BetaFunc( Double_t *x, Double_t *par)
{
  return TMath::BetaIncomplete(.5, x[0], 11-x[0]);
}