## 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…