[TheForge] lamp shade

[xlch58 at swbell.net]

Andy Gladish wrote:
> Dave, the way I visualise this kind of thing is to take the extreme cases:
> in a cubic lampshade, the angle would be simply 90 deg. In a very flattened
> out lampshade, the angle pieces would be practically lying on the table,
> with their spines sticking up in the air- obviously not making the correct
> angle to one another.
> But it's embarrassing to go in a short 12 yrs. from doing calculus daily to
> being so non-fluent in trig that I just shrug at Janet's question and say, I
> also have no idea how to derive the correct angle. (;_*)
>
> Ries- thanks for your ideas and kind offer. I'll try your suggestion and
> beat on it and see if it submits to a logical argument in the shape of a
> hammer. If not, I get to learn how to use a real brake: win/win in any case!
>
> Andy Gladish
> Guemes Island, WA
I have had to do this before and resorted to a web search.  Here are 
some sites with the math.....

http://www.math.toronto.edu/mathnet/questionCorner/miter.html

or

http://www.josephfusco.org/Articles/Dihedral/Dihedral.html

or

http://mathforum.org/library/drmath/view/56462.html

Charles