Live data from Hacker News

Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

math.toronto.edu

111–120 of 122 posts

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#111

I couldn't agree with the last point more. > A course taught as a bag of tricks is devoid of educational value. One year later, the students will forget the tricks, most of which are useless anyway. The bag of tricks mentality is, in my opinion, a defeatist mentality...In an elementary course in differential equations, students should learn a few basic concepts that they will remember for the rest of their lives... I…

you just made me angry at all my college math classes again. grr.

did anyone have an undergrad math education that was NOT like this?

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#112

I couldn't agree with the last point more. > A course taught as a bag of tricks is devoid of educational value. One year later, the students will forget the tricks, most of which are useless anyway. The bag of tricks mentality is, in my opinion, a defeatist mentality...In an elementary course in differential equations, students should learn a few basic concepts that they will remember for the rest of their lives... I…

I had an almost identical experience with my ODE class. This is exactly when I started hating math, and moved out of computer science (which was part of the math department at the university I was at).

It took me a long time to return to learning higher maths, this time on my own according to the needs of my job, which is far less an ideal environment than University.

If ODE contains "a few basic concepts that they will remember for the rest of their lives" I never learned it, and I wonder what those concepts would be.

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#113

I couldn't agree with the last point more. > A course taught as a bag of tricks is devoid of educational value. One year later, the students will forget the tricks, most of which are useless anyway. The bag of tricks mentality is, in my opinion, a defeatist mentality...In an elementary course in differential equations, students should learn a few basic concepts that they will remember for the rest of their lives... I…

Indeed, Rota's approach to teaching seems to mirror the application of mathematics in general...

He acknowledges that concepts have prerequisites, and that certain topics are misleading or dead ends. You might even call the act of building a pedagogical scope and sequence for a topic graph traversal!

I wish I could have taken one of his classes. I wonder if there are other mathemetician/philosophers out there who have taken the problem of teaching as seriously as the math itself.

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#114

Could someone give some examples of applications of numerical methods for solving differential equations that are relevant to a HN crowd? Also, where might I find some introductory material that teaches it well, according to the the suggestions in the OP?

http://longnow.org/essays/richard-feynman-connection-machine...

"By the end of that summer of 1983, Richard had completed his analysis of the behavior of the router, and much to our surprise and amusement, he presented his answer in the form of a set of partial differential equations. To a physicist this may seem natural, but to a computer designer, treating a set of boolean circuits as a continuous, differentiable system is a bit strange. Feynman's router equations were in terms of variables representing continuous quantities such as "the average number of 1 bits in a message address." I was much more accustomed to seeing analysis in terms of inductive proof and case analysis than taking the derivative of "the number of 1's" with respect to time. Our discrete analysis said we needed seven buffers per chip; Feynman's equations suggested that we only needed five. We decided to play it safe and ignore Feynman.

The decision to ignore Feynman's analysis was made in September, but by next spring we were up against a wall. The chips that we had designed were slightly too big to manufacture and the only way to solve the problem was to cut the number of buffers per chip back to five. Since Feynman's equations claimed we could do this safely, his unconventional methods of analysis started looking better and better to us. We decided to go ahead and make the chips with the smaller number of buffers.

Fortunately, he was right. When we put together the chips the machine worked. The first program run on the machine in April of 1985 was Conway's game of Life."

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#115
I somehow managed to get a bachelor's in mathematics without ever taking a DE class (snuck through on a year when program requirements were being rewritten). Everyone I've ever told this to has been aghast, and yet when I ask what I missed out on, no one really has a response other than "I thought everyone had to take it".

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#116
post #59

I would be very curious to see if Gian Carlo Rota had anything to say about Stephen Strogatz's view on this. Strogatz's text (which was written three years before this article, right before he left MIT), is much beloved by many scientists and engineers, but most mathematician's will have complaints about it.

Do you have a link?

I believe he's referring to Strogatz's introductory textbook "Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering".

Amazon link: http://www.amazon.com/Nonlinear-Dynamics-Chaos-Applications-...

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#117

Where can I find an expansion of the intuitive explanation given for integrating factors? > It is of the utmost importance to explain the relation between the solutions of the differential equation and the solutions of the system. The solutions of the system are trajectories, they are parametric curves endowed with a velocity given by the vector field. The solutions of the corresponding differential equation are inte…

Here's an attempted expansion. If you have an equation of the form dy/dx = f(x) and you want "solve" it, what you are typically looking for is to write y = g(x), right? In other words, the solution to this differential equation is some curve in the x-y plane. This applies more generally, e.g. to situations where you end up with an "implicit" solution like h(y) = g(x): you still get an equation relating x and y which…

It helped, thanks!

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#118

I couldn't agree with the last point more. > A course taught as a bag of tricks is devoid of educational value. One year later, the students will forget the tricks, most of which are useless anyway. The bag of tricks mentality is, in my opinion, a defeatist mentality...In an elementary course in differential equations, students should learn a few basic concepts that they will remember for the rest of their lives... I…

Nothing so quickly emphasizes that a bag of tricks can turn into actual math more than a linear algebra course. In a math degree you can literally take the same course twice. At a first year level you will learn to perform all these tricks with matrices and get a hint of inner product spaces. In 2nd or 3rd year you'll do the reverse and justify why matrix algebra works in the first place. But the harder a subject, th…

Illustrated: http://www.wastedtalent.ca/node/716

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#119
Very late to the conversation, but I emailed this to my uncle and he wrote back:

At ANSTO I worked with solution of simultaneous first order differential equations, as arose from Newtons law of cooling for a 4-body calorimeter. That was fun.

Re: Ten lessons I wish I had learned before teaching differential equations (1997) [pdf]

#120
post #95

+1 to teaching concepts - but I don't agree with the author's opposition to word problems and learning to apply a "bag of tricks". I'd argue that "deciphering vaguely-phrased word problems and figuring out which of a selection of tricks to apply" is the MOST transferrable skill somebody can take away from a math class, because it's a major component of working in lots of other fields. For instance, the biggest diffic…

I agree, but I think the "word problems" the author was referring to are much lower quality than the ones you're thinking of. I imagined some highly-contrived exercises where all of the relevant information is already pre-processed for you, removing any need for problem decomposition. For example, "if the angle between the ground and a tree's shadow is 45 degrees and a 50 ft tall telephone pole that's 10 ft away from the tree casts a shadow..." (substitute a similar differential equation problem). As you point out, half the fun is defining a problem and breaking it down, and these kinds of word problems don't give you a chance to do that.
Post reply on HN