//ԲĻ  
public void drawCircleArc(IPoint point,double r)
        { 
          //Բ
            IPoint pPoint = point;
            IConstructCircularArc pConstructCircularArc = new CircularArcClass();//Բ
            pConstructCircularArc.ConstructBearingRadiusAngle(pPoint,0,false,r,Math.PI*4/3);
            ICircularArc pCircularArc = pConstructCircularArc as ICircularArc;//תԲ
            ISegment pSegment = pCircularArc as ISegment;//תɲ֣
            ISegmentCollection pSegmentCollection = new RingClass();//
            object o = Type.Missing;
            pSegmentCollection.AddSegment(pSegment,ref o,ref o);
            IRing pRing = pSegmentCollection as IRing;//תɻ
            IGeometryCollection pGeometryCollection = new PolygonClass();
            pGeometryCollection.AddGeometry(pRing,ref o,ref o);
            //Բʾ
            IElement pElement = new CircleElementClass();
            pElement.Geometry = pGeometryCollection as IGeometry;
            IGraphicsContainer pGraphicsContainer = axMapControl1.ActiveView.GraphicsContainer;
            pGraphicsContainer.AddElement(pElement,0);
            axMapControl1.Refresh();
        }