Equation 9, Capacitance of a Toroid

Greetings Everyone,

   My name is Jim Watson.  I am a student (non-traditional) at the University of West Florida in Pensacola, Florida;  in the Electrical Engineering Technology program.  "Non-traditional" is a euphamism which means that I am a bit older than the normal student.  I am writing a paper on Nikola Tesla and the Wireless Transmission of Power;  I am designing and building a Tesla Coil as part of the same project.

   The equation regarding the capacitance of a toroid. the one contributed by Bert Pool, is not entirely clear to me.  There is a numer 2 in the numerator of the radicand that I can not place with 100% certianty;  this is because the formula has always arrived in a slightly jumbled form, and I have to reconstruct it.

   The two appears to square 2pi;  it appears to be (2pi)^2.  Is this correct?  The remainder of the equation is very clear.  I would also appreciate any comments on the origin of this formula.


                          Jim Watson