绕圈跑

var r=50;//半径
var centerx=300;//圆心
var centery=300;
var i=0;
function ballMove(evn:Event)
{
        ball_mc.x=centerx+Math.sin(i*2*Math.PI/180)*r;
        ball_mc.y=centerx+Math.cos(i*2*Math.PI/180)*r;
        i++
}

ball_mc.addEventListener(Event.ENTER_FRAME,ballMove);