ABSTRACT
This is followed by (or interleaved with, depending on how you decide to read the chapter) a lot of exploratory questions in Section 15.4. Some of the more challenging ideas are reviewed in Section 15.5, and then of course there are problems to think about. Along the way, we will need to introduce new ideas, new notations, and new sets… and we will even leave the realm of discrete mathematics, though just for a minute or two.
