1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution Because we are only looking at a cross section, I tried to reduce 5.3 down to just being a function of R and Theta. However I reasoned that there should be, based on this problem, no dependence on Theta either, so I figured I could reduce 5.3 down to just being which gives the differential equation and has the simple solution of However, this can not really be related back to the to answer that they give me at the start of the problem. I then guessed that means that this problem does some how related to Theta, which means I need to use However, I am unsure of how to solve this equation. I see mentions of the bessel function, however, I don't see how equation 12.9 relates to that function, as I am missing the x^2 term.