Tau version: https://en.wikipedia.org/wiki/File:Circle_radians_tau.gif

I was skeptical, but tentatively convinced by the end of the section on the hypersphere volume/surface area.

I don't think it's worth actually changing things, but if we can accept that 2pi is a more natural constant than pi, then it should help us write more sensible formulas, even if the symbol tau isn't used.

Thanks for this. Tau seems nice, I'll try using it from now on and see if it makes things simpler (judging from what I've seen so far, I'm optimistic about it).