获取任意位置与圆直径形成的等腰三角形的底边与圆的交点的坐标

 1package
 2{
 3    import flash.display.Sprite;
 4    import flash.events.MouseEvent;
 5    
 6    [SWF(width=400,height=400)]
 7    public class SimpleSample5 extends Sprite
 8    {
 9        private var _centerX:Number;
10        private var _centerY:Number;
11        private var _radius:Number = 80;
12        
13        public function SimpleSample5()
14        {
15            _centerX = stage.stageWidth/2;
16            _centerY = stage.stageHeight/2;
17            draw();
18            drawTriangle(0, 0);
19            stage.addEventListener(MouseEvent.MOUSE_MOVE, mouseMoveHandler);
20        }
21        
22        private function draw():void
23        {
24            graphics.clear();
25            graphics.lineStyle(1);
26            graphics.moveTo(0, stage.stageHeight/2);
27            graphics.lineTo(stage.stageWidth, _centerY);
28            graphics.moveTo(_centerX, 0);
29            graphics.lineTo(_centerX, stage.stageHeight);
30            graphics.drawCircle(_centerX, _centerY, _radius);
31        }
32        
33        private function drawTriangle($mouseX:Number, $mouseY:Number):void
34        {
35            var __dx:Number = _centerX - $mouseX;
36            var __dy:Number = _centerY - $mouseY;
37            var __distance:Number = Math.sqrt(__dx*__dx + __dy*__dy);
38            //计算点击处与圆心夹角的角度并在坐标系中旋转90度
39            var __radian:Number = Math.atan2(__dy, __dx) - Math.PI/2;
40            var __x2:Number = _radius * Math.cos(__radian);
41            var __y2:Number = _radius * Math.sin(__radian);
42            graphics.moveTo(_centerX, _centerY);
43            graphics.lineTo($mouseX, $mouseY);
44            graphics.lineTo(_centerX+__x2, _centerY+__y2);
45            graphics.lineTo(_centerX, _centerY);
46            graphics.lineTo(_centerX-__x2, _centerY-__y2);
47            graphics.lineTo($mouseX, $mouseY);
48        }
49        
50        private function mouseMoveHandler(evt:MouseEvent):void
51        {
52            draw();
53            drawTriangle(mouseX, mouseY);
54        }
55    }
56}