FTransMain := TTranslator.Create;
  FTransDeriv :=  TTranslator.Create;

  vName := 'x';
  vValue := 1.0;
  FTransMain.Add(vName, vValue);
  FTransDeriv.Add(vName, vValue);

  try
    if FTransMain.CheckSyntax(f) then
    begin
      df := FTransMain.Derivative(f,'x');

      if FTransDeriv.CheckSyntax(df) then
      begin
        for i := -xrange to +xrange do
        begin
          // get Y value of the function for a given X value
          FTransMain.Variables['x'].Value := i;
          v := FTransMain.Calculate(f);
          // add the Y point to the XY chart series 1
          AChart.Series[0].AddXYPoint(i,v.AsExtended);

          // get Y value of the derivative function for a given X value
          FTransDeriv.Variables['x'].Value := i;
          v := FTransDeriv.Calculate(df);
          // add the Y point to the XY chart series 2
          AChart.Series[1].AddXYPoint(i,v.AsExtended);
        end;
      end;
    end;
  finally
    FTransMain.Free;
    FTransDeriv.Free;
  end;