Геометрический вопрос

[silin]

public class Main extends Sprite
{
	private var gun:Sprite;
	private var target:Sprite;
 
	private var ab:Number = 50;
	private var ad:Number = 80;
 
	public function Main():void
	{
		gun = new Sprite();
		target = new Sprite;
 
		target.graphics.beginFill(0x80FF80);
		target.graphics.drawCircle(0, 0, 10);
 
		gun.graphics.lineStyle(10, 0xFF8080);
		gun.graphics.lineTo(ad, 0);
		gun.graphics.lineTo(ad, -ab);
		gun.graphics.lineStyle(0, 0xC0C0C0);
		gun.graphics.lineTo(ad, -500);
		gun.x = 200;
		gun.y = 200;
 
		addChild(target);
		addChild(gun);
		addEventListener(Event.ENTER_FRAME, enterFrame);
	}
 
	private function enterFrame(e:Event):void
	{
		target.x = mouseX;
		target.y = mouseY;
 
		var tP:Point = new Point(target.x, target.y);
		var gP:Point = new Point(gun.x, gun.y);
		// расстояние
		var dist:Number = Point.distance(tP, gP);
		// направление
		var dir:Number = Math.atan2(tP.y - gP.y, tP.x - gP.x);
		// поправка
		var w:Number = Math.asin(ad / dist);
 
		gun.rotation = 180 / Math.PI * (dir - w) + 90;
 
	}
 
}