package {
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.geom.Point;
 
    public class Cosines extends Sprite {
 
        private var seg0:Segment;
        private var seg1:Segment;
        private var seg0Width:uint=80;
        private var seg1Width:uint=100;
 
        //用于保存上次自由端的dx,dy值
        private var dxOld:Number=0;
        private var dyOld:Number=0;
 
        public function Cosines() {
            init();
        }
 
        private function init():void {
            seg0=new Segment(seg0Width,10,0xff0000);
            addChild(seg0);
            seg1=new Segment(seg1Width,20,0x0000ff);
            addChild(seg1);
            seg1.x=stage.stageWidth/2;
            seg1.y=stage.stageHeight/2;
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }
 
        private function onEnterFrame(event:Event):void {
            var dx:Number=mouseX-seg1.x;
            var dy:Number=mouseY-seg1.y;
            if (dx==dxOld&&dy==dyOld) {
                //trace("已经调整到位了!");
                return;//直接返回，不作处理了
            }
            dxOld=dx;
            dyOld=dy;
            //trace(dx,dy);
            var dist:Number=Math.sqrt(dx*dx+dy*dy);
            var a:Number=seg1Width;
            var b:Number=seg0Width;
            if (dist>=(a+b)) {
                //trace(dist,a+b);
                seg1.rotation=seg0.rotation=Math.atan2(dy,dx)*180/Math.PI;
            } else {
                var c:Number=Math.min(dist,a+b);
                var B:Number = Math.acos((b * b - a * a - c * c) / (-2 * a * c));
                var C:Number = Math.acos((c * c - a * a - b * b) / (-2 * a * b));
                var D:Number=Math.atan2(dy,dx);
                seg1.rotation = (D + B) * 180 / Math.PI;
                var E:Number=D+B+Math.PI+C;
                seg0.rotation=E*180/Math.PI;
            }
            seg0.x=seg1.getPin().x;
            seg0.y=seg1.getPin().y;
        }
    }
}