Yesterday we (my family and I) drove to Allentown, PA to go to the Da Vinci Science Center. We’d never been there before, and would have been interested in going anyway, but the reason for going now is that they are hosting the Math Midway exhibit (until January 6, 2010). More specifically, my son and…

# Month: December 2009

## Showing two expressions are equal: stop the madness

I know that most you who read my blog teach mathematics at either the high school or college level. I’d like to ask you a question (at the end of the post). It is about how our schools teach students to show that two mathematical quantities are equal. This has bothered me ever since I…

## Twitter and Origami

Twitter is amazing. Two nights ago I watched the PBS documentary on origami, Between the Folds. Yesterday morning when I got to my office I made the following post on Twitter: In the next 12 hours I was flooded with suggestions, comments, and links. Here are some of the book titles and links that people sent…

## Edublog award nomination

Wow, what an honor! My blog is now on the short list of Best Teacher Edublogs for 2009. I’d like to thank Brenda Landis for the nomination. Please head over to the site to vote for your favorite blogs! Voting ends Wednesday, December 16. By the way, I also encourage you to vote for Chris…

## Mathematical holiday cookies at Starbucks

When I was in Starbucks the other day my eyes were drawn to the cookie display, for what did I see, but a row of cookies all decorated with ‘s! Upon closer inspection I discovered, to my disappointment, that it was not the Greek letter, but the red scarf of a polar bear. (As Homer…

## Euler’s formula in a children’s book

As you may know, I wrote a book on Euler’s polyhedron formula. (Euler’s formula says that every polyhedron with V vertices, E edges, and F faces satisfies V-E+F=2.) I gave a talk recently during which I lamented that kids aren’t taught this beautiful theorem; after all, it relies only on counting, addition, and subtraction. After…

## Cobweb plots for the logistic map: a Geogebra applet

A few days ago I posted Geogebra applets illustrating discrete dynamical systems. I was using these in a differential equations lecture that I gave. In the next lecture I showed the students how to draw cobweb plots for 1-dimensional discrete dynamical systems. A discrete dynamical system is a function in which the range is a…

## An applet illustrating a continuous, nowhere differentiable function

Open any calculus book and you will find a discussion about how differentiability implies continuity, but continuity does not imply differentiability. The absolute value function is the standard example of a continuous function that is not differentiable (at ). The inquisitive student may ask: how bad can continuous, nondifferentiable functions get? Can we make a…

## Applet for discrete dynamical systems

I’m teaching the last two weeks of one of my colleagues’ Differential Equations course. I’m leading the class through a chapter on discrete dynamical systems. In preparation for the first lecture I created a couple of java applets using Geogebra. I thought others might be interested in them, so I’m linking to them here. The…