void formula1()
{
   TCanvas *c1 = new TCanvas("c1", "Example with Formula", 200, 10, 700, 500);
   //
   // We create a formula object and compute the value of this formula
   // for two different values of the x variable.
   //
   auto form1 = new TFormula("form1", "sqrt(abs(x))");
   form1->Eval(2);
   form1->Eval(-45);
   //
   // Create a one dimensional function and draw it
   //
   auto fun1 = new TF1("fun1", "abs(sin(x)/x)", 0, 10);
   c1->SetGridx();
   c1->SetGridy();
   fun1->Draw();
   c1->Update();

}