Altruism: Morally Neutral?

As I read your last post, it occurred to me that one thing we haven't established is whether altruism is a good thing, a bad thing, or a neutral thing. I think the general view on altruism is that it's a admirable thing ... but is that good, bad or neutral?

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We have reached summer here in the desert southwest. Daily temperatures commonly hit the century mark (100 degrees Fahrenheit; 38 degrees Celcius). It's 10:45am and it's already 90F. But, surprisingly, it's not really that uncomfortable.

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Imagine a room, with four walls and a ceiling. Assume the walls are plumb vertically, and square to each other and the ceiling. Now imagine a piece of crown molding set at 45-degrees to the wall and the ceiling to which it attaches. That piece of crown molding runs up to a corner formed by two walls and the ceiling. On the adjacent wall is also a piece of crown molding, of the same size and dimension, also set at 45 degrees to its wall and ceiling.

Question: what is the mathematical function that defines the relationship of the compound mitre cut that is required make the two pieces of molding match perfectly at the corner?

I've never been able to figure that out. Which explains why I've always shied away from installing crown molding. It gets even more complicated when the walls and ceiling are not plumb and square. The next time you see a finish carpenter, tip your hat ... those folks do amazing things.