My virtual seminar goes live

I love my job—I teach at a small, highly selective liberal arts college. It is a great place to work. But one thing I miss from my days at big research universities is the constant stream of research mathematicians who give seminars and colloquia.  I am within two hours of Philadelphia, Baltimore, Washington DC, and…

Bubbles with knotted boundaries

We can think of a mathematical knot as a knotted piece of string (or in our case, wire) with its free ends joined. Examples are shown below. There is a remarkable theorem that every knot can be realized as the boundary of a surface. Moreover, Herbert Seifert produced a very simple algorithm for constructing an orientable…

The area versus the circumference of a circle

I just found this stop motion animation that I made last year when I was playing around with the iStopMotion software. So I uploaded it to YouTube and posted it here for you all to see. It is not the highest quality, but it was fun to make. It shows the Greek method of relating…

Multiplication of multi-digit numbers: a visual approach

Here’s a neat video showing a visual approach to multiplying muli-digit numbers. The algorithm is just a visual representation of the standard mechanical procedure that we all know, but somehow computing the product from these criss-crossed lines makes it look easier. One problem I see is that the algorithm may lead to confusion if there…

Units are important

This made me laugh. My favorite line is “Well, I mean, it’s obviously a difference of opinion.” [via failblog]

Definition of continuity video

Thank you to Dansmath for turning me on the website xtranormal. It allows you to create your own animated videos. It is easy and fun. You can choose the characters, the scene, the camera angles, the gestures and facial expression, music, etc. They do the voices for you—you just type the script. Here are some of Dan’s videos….

Multiple choice questions in mathematics

It must be exam time. Discussions of multiple-choice test questions are in the air. Terrence Tao has a nice post about multiple choice questions in mathematics (it is a follow-up to this post of his). He writes about the pros and cons of giving multiple choice questions in a mathematics class. For example: These quizzes give a…

Twittering Division by Zero

I’ve been on Twitter for a few months, posting unimportant details about my life. But I’ve decided to repurpose that service and make it another outlet for my Division by Zero blog. In case you are not aware, Twitter is a micro-blogging service that allows you to publish posts (“tweets”) of up to 140 characters at…

Honda Civic plays the William Tell Overture

American Honda paid for a viral marketing campaign in Lancaster, CA for the Honda Civic. They cut grooves in the road so that when a car drives over the road at 55 mph (in a Honda Civic, presumably), it will play Rossini’s William Tell Overture (yes, that’s the Lone Ranger theme song). The “debut” of…

Folding a golden rectangle

Recently I wrote about the mathematics of cutting and folding paper and about the golden ratio, . Here’s a video that brings these two ideas together. We see how to create a golden rectangle (a rectangle for which the ratio of the sides is ) by folding a piece of paper. [via Anthony Brand’s maths…