ball._x = 100;
ball._y = 100;
var xDis = ball._x - 10;
var yDis = ball._y - 20;
var r = Math.sqrt ((xDis * xDis) + (yDis * yDis));
var degree = 60;
var speed = 0.1;
ball.onEnterFrame = function () {
this._x = Math.cos (degree) * r;
this._y = Math.sin (degree) * r;
degree = degree + speed;
};