procedure TForm1.Button1Click(Sender: TObject);
const
 PI = 3.14159;
var
 X,Y: Real;
 PX,PY: Longint;
 Offset: Longint;
 HalfHeight: Longint;
begin
 HalfHeight := Form1.Height div 2;
 Offset := 0;
 for Offset := -10 to 10 do
 begin
  PX := 0;
  while PX < Form1.Width do
  begin
   X := PX * (2*PI/Form1.Width);
   Y := sin(X);
   PY := trunc(0.7 * Y * HalfHeight) + HalfHeight + (Offset*10);
   if (PX = 0) then Canvas.MoveTo(PX, PY);
   Canvas.LineTo(PX, PY);
   PY := trunc(0.7 * Y * HalfHeight) + HalfHeight + ((Offset-1)*10);
   Canvas.LineTo(PX, PY);
   PX := PX + 15;
  end;
 end;
end;