图形旋转

public Form1()
        {
            InitializeComponent();
        }
        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            Graphics g = e.Graphics;
            Pen p = new Pen(Color.Black, 2);            PointF[] points = { new PointF(25.0F, 35.0F), new PointF(110.0F, 115.0F), 
                                  new PointF(40.0F, 120.0F),
                                new PointF(25.0F, 35.0F) };
            g.DrawLines(p, points);
            g.RotateTransform(30.0F);
        }请问这个旋转怎么实现？