lab

Graphics gr;
        int x, y, a, b, dx, x0, y0, x1, y1, R, y2, x2;
        double fi, dfi, fi1;
        private void button1_Click(object sender, EventArgs e)
        {
            gr = pictureBox1.CreateGraphics();
            gr.Clear(Color.White);
            x0 = pictureBox1.Width / 2;
            y0 = pictureBox1.Height / 2;
            R = 100;
            x1 = x0 + R;
            y1 = y0;
            x2 = x0;
            y2 = y0-R;
            fi = 0;
            fi1 = 80;
            dfi = Math.PI / 30;
            gr.DrawLine(Pens.DarkBlue, x0, y0, x1, y1);
            gr.DrawLine(Pens.DarkBlue, x0, y0, x2, y2);
            timer1.Start();

        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            gr.DrawLine(Pens.White, x0, y0, x1, y1);
            gr.DrawLine(Pens.White, x0, y0, x2, y2);
            fi = fi + dfi;
            fi1 = fi1 + dfi;
            x2 = (int)(x0 + R * Math.Cos(fi1));
            y2 = (int)(y0 + R * Math.Sin(fi1));
            x1 = (int)(x0 + R * Math.Cos(fi));
            y1 = (int)(y0 + R * Math.Sin(fi));
            gr.DrawLine(Pens.DarkBlue, x0, y0, x1, y1);
            gr.DrawLine(Pens.DarkBlue, x0, y0, x2, y2);
        }