curveToとMath.tanで円を描く

/**
 * Copyright hacker_szoe51ih ( http://wonderfl.net/user/hacker_szoe51ih )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/ryA8
 */

// forked from hacker_szoe51ih's forked from: forked from: forked from: flash on 2010-5-2
// forked from hacker_szoe51ih's forked from: forked from: flash on 2010-5-2
// forked from hacker_szoe51ih's forked from: flash on 2010-5-2
// forked from hacker_szoe51ih's flash on 2010-5-2
package {
    import flash.display.*;
    [SWF(width = "465", height = "465", frameRate = "30", backgroundColor = "#000000")]
  
    public class DrawCircle3 extends Sprite {
 	public var centerX:Number=100;
 	public var centerY:Number=100; 	
    	public var hankei:Number=50;
    	
        public function DrawCircle3() {
        	
       //graphics.beginFill(0x2222dd);
       graphics.lineStyle(2,0x00ff22);
       graphics.moveTo(centerX+hankei,centerY);//描画開始位置に移動
       //graphics.curveTo(hankei+centerX,Math.tan(Math.PI/8)*hankei+centerY,Math.sin(Math.PI/4)*hankei+centerX,Math.sin(Math.PI/4)*centerY)
       // graphics.curveTo(400,100,400,400);コントロールポイント(400,100)アンカーポイント(400,400)
       //時計回りに円を描く
       //アンカーポイントの座標はsinにしても同じ
       graphics.curveTo(centerX+hankei,centerY+Math.tan(Math.PI/8)*hankei,centerX+Math.cos(Math.PI/4)*hankei,centerY+Math.sin(Math.PI/4)*hankei);
       graphics.curveTo(centerX+Math.tan(Math.PI/8)*hankei,centerY+hankei,centerX,centerY+hankei);
       graphics.curveTo(centerX-Math.tan(Math.PI/8)*hankei,centerY+hankei,centerX-Math.cos(Math.PI/4)*hankei,centerY+Math.sin(Math.PI/4)*hankei);
       graphics.curveTo(centerX-hankei,centerY+Math.tan(Math.PI/8)*hankei,centerX-hankei,centerY);
       graphics.curveTo(centerX-hankei,centerY-Math.tan(Math.PI/8)*hankei,centerX-Math.cos(Math.PI/4)*hankei,centerY-Math.sin(Math.PI/4)*hankei);
       graphics.curveTo(centerX-Math.tan(Math.PI/8)*hankei,centerY-hankei,centerX,centerY-hankei);
       graphics.curveTo(centerX+Math.tan(Math.PI/8)*hankei,centerY-hankei,centerX+Math.cos(Math.PI/4)*hankei,centerY-Math.sin(Math.PI/4)*hankei);
       graphics.curveTo(centerX+hankei,centerY-+Math.tan(Math.PI/8)*hankei,centerX+hankei,centerY);  
       graphics.endFill();          
        
            
        }
    }
}