画椭圆

package 
{

    import flash.display.Sprite;

    public class Ball extends Sprite
    {

        public var radius:Number;
        public var color:uint;

        public function Ball(radius:Number=10,color:uint=0Xff0000)
        {
            this.radius = radius;
            this.color = color;
            draw();
        }

        public function draw():void
        {
            graphics.beginFill(color);
            graphics.drawCircle(0,0,radius);
            graphics.endFill();
        }

    }

}

package 
{
    import flash.display.Sprite;
    import flash.events.Event;

    public class Main extends Sprite
    {
        private var ball:Ball;
        private var angle:Number=0;
        private var centerX:Number = 300;
        private var centerY:Number = 200;
        private var radiusX:Number = 200;
        private var radiusY:Number = 100;
        private var speed:Number = 0.1;
        private var s:Sprite;

        public function Main()
        {
            init();
        }

        private function init():void
        {
            //trace(Math.sin(0));=0
            //trace(Math.cos(0));=1
            ball = new Ball  ;
            addChild(ball);
            ball.x = 300;
            ball.y = 300;
            s=new Sprite;
            addChild(s);
            s.graphics.lineStyle(1,0xff0000);
            s.graphics.moveTo(ball.x,ball.y);
            addEventListener(Event.ENTER_FRAME,_onEnterFrame);
        }

        private function _onEnterFrame(e:Event):void
        {
            ball.x = centerX + Math.sin(angle) * radiusX;
            ball.y = centerY + Math.cos(angle) * radiusY;
            s.graphics.lineTo(ball.x,ball.y);
            angle +=  speed;
        }
    }
}