Как нарисовать движение точки по оси эллипса?

  float a = 250, b = 100;
  int i = ClientWidth / 2, j = ClientHeight / 2;
  Canvas->MoveTo(i - a, j);
  Canvas->LineTo(i + a, j);
  Canvas->MoveTo(i, j - b);
  Canvas->LineTo(i, j + b);
  for (float t = 0; t <= 2 * M_PI; t += 0.001)
    Canvas->Pixels[i + a * cos(t)][j + b * sin(t)] = clRed;

  for (float t = 0; t <= 2 * M_PI; t += 0.001)
    Canvas->Pixels[i + a * cos(t)][j + b * sin(t)] = clRed;

void __fastcall TForm3::Timer1Timer(TObject *Sender)
{
    double a,b;
    double t,f;
    int x,y;
 
    a = StrToFloat(LabeledEdit1->Text);
    b = StrToFloat(LabeledEdit2->Text);
 
    int i = ClientWidth / 2, j = ClientHeight / 2;
 
    Canvas->Pen->Color=clBtnFace;
    Canvas->Ellipse(x-25,y-25,x+25,y+25);
 
    x = a * cos(f);
    y = b * sin(f);
 
    Canvas->Pen->Color=clBlack;
    Canvas->Ellipse(x-25,y-25,x+25,y+25);
 
    f += 0.1;
    if (f >= 2*M_PI)
        f = 0;
}

void __fastcall TForm3::Timer1Timer(TObject *Sender)
{
    double a,b;
    double t,f;
    int x,y;
 
    a = StrToFloat(LabeledEdit1->Text);
    b = StrToFloat(LabeledEdit2->Text);
 
    int i = ClientWidth / 2, j = ClientHeight / 2;
 
    Refresh();
    Canvas->Pen->Color = clBlue;
    Canvas->Brush->Color = Color;
    Canvas->Ellipse(((i + a * cos(f))-25), ((j + b * sin(f))-25), ((i + a * cos(f))+25), ((j + b * sin(f))+25));
    f += 0.01;
    for (double l = 0; l <= 2*M_PI; l += 0.001)
        Canvas->Pixels[i + a * cos(l)][j + b * sin(l)] = clBlack;
}

void __fastcall TForm3::Timer1Timer(TObject *Sender)
{
    Timer1->Interval = 300;
    Timer1->Enabled = 1;
 
    double a,b;
    double t;
    double x,y;
 
    a = StrToFloat(LabeledEdit1->Text);
    b = StrToFloat(LabeledEdit2->Text);
 
    int i = ClientWidth / 2, j = ClientHeight / 2;
 
    x = i + a * Cos(f);
    y = j + b * Sin(f);
 
    Canvas->Pen->Color = clRed;
    Canvas->Brush->Color = Color;
    if (a <= 260){
        Canvas->Ellipse((i - 2*a/3 - 20), (j - 20), (i - 2*a/3 + 20), (j + 20));
    }
    else {
        Canvas->Ellipse((i - 2*a/3 - 60), (j - 60), (i - 2*a/3 + 60), (j + 60));
    }
 
    Canvas->Pen->Color = clBlue;
    Canvas->Brush->Color = Color;
    if (a <= 260) {
        Canvas->Ellipse((x - 2.5), (y - 2.5), (x + 2.5), (y + 2.5));
    }
    else {
        Canvas->Ellipse((x - 15), (y - 15), (x + 15), (y + 15));
    }
 
    f += 0,01;
 
    /*for (double l = 0; l <= 2*M_PI; l += 0.001)
        Canvas->Pixels[i + a * cos(l)][j + b * sin(l)] = clBlack;  */
}

__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
  Timer1->Enabled = 1;
  Timer1->Interval = 100;
  Canvas->Brush->Color = clBlue;
  DoubleBuffered = 1;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Timer1Timer(TObject *Sender)
{
  Refresh();
  float a = 250, b = 100, x, y;
  int i = ClientWidth / 2, j = ClientHeight / 2, r = 5;
  Canvas->Pen->Color = clBlack;
  Canvas->MoveTo(i - a, j);
  Canvas->LineTo(i + a, j);
  Canvas->MoveTo(i, j - b);
  Canvas->LineTo(i, j + b);
  for (float t = 0; t <= 2 * M_PI; t += 0.01)
    Canvas->Pixels[i + a * cos(t)][j + b * sin(t)] = clRed;
 
  Canvas->Pen->Color = clBlue;
  x = i + a * cos(Tag / 180. * M_PI);
  y = j + b * sin(Tag / 180. * M_PI);
  Canvas->Ellipse(x - r, y - r, x + r, y + r);
  Tag++;
}