как сделать, чтобы график начинал чертить с начала координат delphi

[малина12]

var
Form1: TForm1;
x,y:real;
px,py:longint;

n,m:integer;
implementation

{$R *.dfm}

procedure TForm1.Button3Click(Sender: TObject);

begin
Timer1.Enabled:=false;
n:= image1.Width div 2;
m:= image1.height div 2;
image1.Canvas.MoveTo(0,m);
image1.Canvas.Pen.Color:=clblack;
image1.Canvas.LineTo(image1.Width,m );
image1.Canvas.MoveTo(n,0);
image1.Canvas.Pen.Color:=clblack;
image1.Canvas.LineTo(n,image1.heigh t);

end;

procedure TForm1.FormCreate(Sender: TObject);
begin
Timer1.Enabled:=false;
image1.Canvas.Brush.Color:=clwhite;
image1.Canvas.Rectangle(0,0,image1. Width,image1.height);
end;

procedure TForm1.Timer1Timer(Sender: TObject);

begin
px:=px+1;
x:= px/image1.Width;
y:= sqrt(x);
py:=trunc(image1.height-(y+1)*image1.height/2);
image1.Canvas.Pixels[px,py]:=0;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
Timer1.Enabled:=true;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
Timer1.Enabled:=false;
end;

end.

[Black Fregat]

А как сейчас?