I am looking for some resources (books, Web sites, etc.) for teaching calculus students about inverse functions, using the ideas of codomain and onto functions (as well as one-to-one functions, of course). This is the way that most mathematicians think about inverse functions, and I don't think it is that difficult. I have looked at some popular calculus texts and some Web sites and they seem to completely ignore the concepts of codomain (or "target") of a function and onto functions. Maybe students can get by with this in Calc I, but in more advanced courses they will either have trouble or their instructors will have to waste time teaching them these basic concepts.
More info: I'm teaching Calc I. The books I seen don't mention codomain at all, they just define domain, range, and one-to-one function, then they define the inverse of a one-to-one function $f$ as the function $f^{-1}$ whose domain is the range of $f$, etc. etc. (you all know the rest)
EDIT: Since all the functions we'll be inverting this semester have codomain $\mathbb{R}$, I'm considering just doing it the way the calc books do it. My students may not see any purpose to defining a codomain, and I'm afraid that expressly giving a codomain for each example might confuse them because they have not seen real-valued functions treated that way before. Still, I think that when calc books define the idea of a function early in the book, they should introduce the important and simple concept of codomain.