Math 560
Spring, 2006
Course wrapup

Your assignment

This last homework (if that's what it should be called) has three parts.

It's due May 9, at the last class. If you provide an envelope addressed to yourself I will return your work with my comments.

  1. Go through all your old homeworks. Pick out a few problems that you got wrong and that you now know how to do, and do them correctly. Turn in the original incorrect work and your new correct revised work, showing clearly what's different and why.

    I don't know quite how many "a few" means. Perhaps half a dozen - but not all alike. If you redo the one in which you show 0 is unique in a ring then don't also redo the one in which you show 1 is unique. If you do one computation showing how to use the Euclidean algorithm to solve ax+by=n (assuming you missed it the first time around) then don't do a second.

    You should only spend time on problems worth spending time on. Some of the ones I asked turned out to be tedious and uninformative. Don't redo one of them, even if you got it wrong the first time - since you still won't learn much by doing it.

  2. Write a short essay in which you reflect on the course. Here are some questions you can consider - but feel free to make up your own, or ignore these. Don't just write an essay in which you devote one paragraph to each one in turn. Organize your thoughts around your experience.

    What did you learn? What was interesting (or boring)? How (if at all) has your attitude toward (some part of) mathematics changed? What do you think you might remember from this course N years from now? What do you think will be useful (in life, thought or your classroom)? How hard did you work? If I teach this course again (or when I discuss it with whoever does teach it next) what should I keep? What should I change (add or subtract)? How might I use the class time better?

  3. (Optional, but I'd like an answer if you can bring yourself to provide one.) What grade do you think you have earned in this course? Why? If you answer this question I will take your answer into account when I assign your grade - but reserve the right to enter a higher (or lower) grade than you think you deserve.


My reflections

I found this one of the most interesting and enjoyable courses I've ever taught. That's because I had the rare opportunity to try to communicate what's beautiful and exciting about mathematics. In most courses that's at best a side effect, while the primary focus is on "covering the syllabus," whatever the syllabus happens to be.

The nominal goal was to do enough abstract algebra to be able to prove the three classic nonconstructability theorems - cube duplication, angle trisection and circle squaring (modulo the irrationality of pi). That matched the goal of the Sethuraman text, which we started out following pretty closely. But shortly after we'd dealt with the definitions of ring and field the book got too dense and (from the students point of view) technical. We pretty much abandoned the book. But we did get to the nonconstructability, more or less following the much more direct argument in Courant and Robbins.

The primary virtue of the way the course started was the way it led us to focus on the "abstract" part of "algebra" (and that is after all what the course should be about). The idea that "the usual rules of arithmetic" might (or might not) apply to objects other than numbers was striking and central. We worked on this by doing lots of computations in various rings (Z mod n, polynomials over an arbitrary ring, Q[sqrt(2)] and Q(sqrt(2)) rather than by proving theorems about rings. (We did do some of that and I would do more next time, but not at the expense of the calculations.)

We studied lots of important topics that I think belong in any high school math teachers repertoire (whether or not they show up in the high school classroom). Many of the students had never seen many of them, or had seen them and forgotten them, so these digressions were very worthwhile. Among the topics:

  1. Fundamental theorem of arithmetic, Euclidean algorithm.
  2. Cardinality, uncountability, diagonalization arguments.
  3. Elementary combinatorics, Pascal's triangle.
  4. The irrationality of sqrt(2).
  5. Euler's theorem, platonic polyhedra.

Homework

For the clearest idea of what we covered, read the homework assignments. I discovered that I could not write those assignments before class, since I could not predict the rate at which we would progress through the material I prepared, nor what important questions (deserving answers) would come up in class. So I took to making up the homework on Wednesday after the Tuesday night class and posting it on the course web page.

A few of the problems asked for proofs (which the students had trouble with throughout and which I did not teach well). But most asked for exploration - guessing theorems by looking for patterns. This worked well - we ended with quadratic reciprocity!

Book reports

Over Spring break I had the students each choose a book (from my library of historical and recreational mathematics) and write a book report - not a summary, but a reflection on whether the chosed book was interesting, perhaps useful in their education as teachers. This exercise was very successful. I would do more of it.

Among the choices:

  1. Flatland
  2. Fantasia Mathematica
  3. The Man Who Knew Infinity
  4. Several arithmetic and algebra texts 50-100 years old
  5. ...

Textbooks

Toward the end of the semester I received a desk copy of An Introduction to Abstract Algebra with Notes to the Future Teacher by Olympia Nicodemi, Melissa A Sutherland, Gary W Towsley. I looked it over and found it promising, so asked several of the students to look at it too. They both thought it would work better than Sethuraman, which we essentially abandoned early in the semester.

Next time I would require Courant and Robbins (this time most of the students bought one at my recommendation). It's back in print in paperback, and good used inexpensive hardbound copies are available on the web.

I think I would also use Hugo Steinhaus' Mathematical Snapshots, just because it the book that first kindled my love of mathematics.

Student population

Nominally, college math majors. Actually ...

How often should the course meet?

Student comments