I have been working through some lecture notes and am quite confused on something. I am trying to understand how to average a quantity over an orbit (keplerianKeplerian) but I am struggling to get a clear idea on this. The notes I am using is: http://www.sns.ias.edu/sites/default/files/isima1.pdf
So I am trying to do the exercise on page 8, but have no idea how to get the solutions shown.