How to calculate the apparent bounding box of a rotated object?

Say I have a MovieClip of a non-rectangular shape. For an example I’ve attached a file called Symbol1.png. In this attached file, I’ve rotated the symbol instance. Of course, this causes the bounding box to rotate as well.

Now say I place that rotated symbol instance inside another symbol. I’ve illustrated this in the attached file called Symbol2.png. Note that the bounding box now includes the overhanging corners of the rotated symbol that is inside.

Is there any practical way to determine the apparent bounding box of Symbol2 without including the corners of Symbol1’s bounding box? I’m trying to zoom and rotate to an automatically calculated size and angle, but this overhang problem is causing a lot of extra space to be included in my final zoomed perspective.

Thanks.