Shadow Box Angles

Dear All:
I have been making shadow box frames here and there for roughly 20 years. I developed some equations for making shadow frames for any number of sides and any number of angles and they are as follows:
Miter Angle = 180/n * cos(shadow angle) Bevel Angle = 180/n * sin(shadow angle)
Now, these equations work over a reasonable range, but are NOT entirely accurate for all angles and # of sides. For instance, they work at shallow angles on almost any number of sides, but fall completely apart on a 3 sided figure - I think that the actual equations are a tensor, but am not entirely sure.
I have done some research and I haven't been able to find a really good shadow box table or a general equation such as the above that actually works. It's extremely frustrating because I finally bought a decent table saw and I can't make a shadow box to save my life!!!!!!
If anyone out there knows of a good table for shadow box data, or has some equations that can get me started. Please help!!!

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