линейные программы

unit Unit1;
 
interface
 
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,math;
 
type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.Button1Click(Sender: TObject);
Var
R1,R2,S:Real;
begin
 R1:=StrTofloat(Edit1.text);
 R2:=StrTofloat(Edit2.text);
 S:=pi*(sqr(R2)-Sqr(R1));
 ShowMessage('Площадь кольца равна '+ FloatToStr(RoundTo(S,-2)));
end;