ActionScript 3.0 :: Calculate Width And Height After Object Rotation

I am tweeing a bunch of rectangles randomly on stage.

Code:
TweenLite.to(thumbArr[i],1,{
x:Math.random () * (stage.stageWidth - thumbArr[i].width),
y:Math.random () * (stage.stageHeight - thumbArr[i].height),
rotation: Math.random () * (60) - 30});

the problem is that after I added random rotation (between -30 and 30 degrees), the corners of my rectangles are still sticking out of the stage at the end of the tween.

If I trace objects width and height after the rotation I get the new values but this still doesnt help me because I am tweening to that rotation.

Code:
mc.rotation = 20;
trace(mc.width);
trace(mc.height);