On 26 May 1999 12:21:54 -0500, Ron Parker wrote:
>I think that the distance between centers is now something like
>2*(r+sqrt(s^2-r^2)*cos(pi/n)).

I would be wrong, however, because I stupidly made the old 
sqrt(a+b)=sqrt(a)+sqrt(b) mistake.  The correct result is even 
uglier than I said it is: 

2*sqrt(r^2+(s^2-r^2)*(cos(pi/n))^2)

>I think the relationship between s and r is something like 
>s^2 = r^2+(2*pi*(R-r)*r/w)^2), where w is the "wavelength" of a single 
>twist.  So s^2-r^2 is (2*pi*(R-r)*r/w)^2 and we get

I don't yet see anything wrong with this part, but the rest of the
derivation is wrong.  Instead we have:

(R-r)^2*(sin(pi/n))^2=r^2+(2*pi*(R-r)*r/w*cos(pi/n))^2

I still don't feel like solving for r. :)

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