public void PaintCircleHand(Graphics g, Pen pen, int point_x, int radius)

        {



            //Graphics g = this.CreateGraphics();

            g.SmoothingMode = SmoothingMode.AntiAlias;

            g.PixelOffsetMode = PixelOffsetMode.HighQuality;



            //更改坐标系统的原点，新原点即为圆心

            g.TranslateTransform(this.Width / 2, this.Height / 2);



            //定义指针坐标

            Point PPoint = new Point();

            Point PSPoint = new Point();



            //根据鼠标X坐标计算指针Y坐标

            //三种情况

            if (point_x <= -radius && point_x >= -radius - 20)

            {

                PPoint.X = -radius - (point_x + radius);

                PPoint.Y = Convert.ToInt32(Math.Sqrt((radius * radius) - (PPoint.X * PPoint.X)));

            }



            else if (point_x >= radius && point_x <= radius + 20)

            {

                PPoint.X = radius - (point_x - radius);

                PPoint.Y = Convert.ToInt32(Math.Sqrt((radius * radius) - (PPoint.X * PPoint.X)));



            }