We use the results collected here repeatedly in the main chapters, but deriving them where they are first needed would interrupt the argument.
They cover the conditions under which the behavior of many heterogeneous households collapses into a single aggregate relationship, a side-by-side comparison of the discrete and continuous time formulations of the Ramsey problem, and a list of the mathematical facts this literature leans on most often (geometric sums and logarithmic approximations, mostly).