第四题答案
function drawCircle(mc:MovieClip, x:Number, y:Number, r:Number):Void
{
mc.moveTo(x+r, y);
mc.curveTo(r+x, Math.tan(Math.PI/8)*r+y, Math.cos(Math.PI/4)*r+x, Math.sin(Math.PI/4)*r+y);
mc.curveTo(Math.tan(Math.PI/8)*r+x, r+y, x, r+y);
mc.curveTo(-Math.tan(Math.PI/8)*r+x, r+y, -Math.cos(Math.PI/4)*r+x, Math.sin(Math.PI/4)*r+y);
mc.curveTo(-r+x, Math.tan(Math.PI/8)*r+y, -r+x, y);
mc.curveTo(-r+x, -Math.tan(Math.PI/8)*r+y, -Math.cos(Math.PI/4)*r+x, -Math.sin(Math.PI/4)*r+y);
mc.curveTo(-Math.tan(Math.PI/8)*r+x, -r+y, x, -r+y);
mc.curveTo(Math.tan(Math.PI/8)*r+x, -r+y, Math.cos(Math.PI/4)*r+x, -Math.sin(Math.PI/4)*r+y);
mc.curveTo(r+x, -Math.tan(Math.PI/8)*r+y, r+x, y);
}