public void Draw_tree(double level, double x, double y, double angle1, double angle2, double coefficient)
        {
            angle1 = angle1 * pi / 180;
            angle2 = angle2 * pi / 180;
            double length = (y - y / 3 * 2);
            double x1 = x, y1 = y / 3 * 2, x2 = x, y2 = y / 3 * 2;
            double xLeft, yLeft, xRight, yRight;
            if (level == 0) graph.DrawLine(pen, (int)x, (int)y, (int)x, (int)(y * 2 / 3));
            else
            {
                xLeft = x1 - length * Math.Cos(pi / 2 - angle1) * coefficient;
                yLeft = y1 - length * Math.Sin(pi / 2 - angle1) * coefficient;
                xRight = x2 + length * Math.Cos(pi / 2 - angle2) * coefficient;
                yRight = y2 - length * Math.Sin(pi / 2 - angle2) * coefficient;

                graph.DrawLine(pen, (int)x1, (int)y1, (int)xLeft, (int)yLeft);
                graph.DrawLine(pen, (int)x2, (int)y2, (int)xRight, (int)yRight);

                x1 = xLeft;
                y1 = yLeft;
                x2 = xRight;
                y2 = yRight;

                Draw_tree(level - 1, x1, y1, angle1, angle2, coefficient);
                Draw_tree(level - 1, x2, y2, angle1, angle2, coefficient);
            }
        }