Joel asks what should one do when one wishes to depart from the textbook.
There are two reasons one might do so. The first, that the instructor
thinks he sees a better way to do something than the textbook does (e.g.
my preference for using a better definition of weight than Hecht uses)
and when one realizes that the textbook is just plain misleading or even
wrong (e.g. problem #138, p. 288 in Hecht Chapter 8, in the section on
conservation of angular momentum). In both kinds of situation I go
ahead and do it my way. A committee picked the textbook; I had no say
in its choice. The difficulty I have is that these kids paid C$100 for
the book, and I knock it. That does constitute a problem.