Have you ever seen the proof that is irrational? If not, I highly recommend heading over to The Math Less Traveled. Blogger Brent Yorgey just posted the last of his six part series in which he gives Ivan Niven’s easy-to-follow 1947 proof of that famous fact. The proof uses only basic calculus.
Three applets illustrating parametric curves
In my multivariable calculus we’re talking about parametric curves. I’m using this applet for displaying parametric curves. You can use predefined curves or enter your own. Although the applet is on my web page, it was created by Marc Renault, a friend who teaches down the road at Shippensburg University. I only tweaked it slightly when…
Why do mirrors reverse right and left but not up and down?
[I apologize to those of you who have been reading my blog for more than a year. I’m reposting something I wrote last year at this time. I was then, and am now, teaching Calculus III, and we just finished discussing the cross product. I ended the conversation by telling my classes how the cross…
Three applets for linear algebra or multivariable calculus
This semester I’m teaching two sections of Calculus III (multivariable calculus) and I happen to be teaching the first four weeks of Linear Algebra. The first couple weeks of both courses cover properties of vectors in Rn. (Of course, just to confuse the instructor and the students who happen to be in both classes, the…
Division by Zero listed as one of 50 Best Blogs for Education Leaders
This morning I was pleased to discover that my blog appears on OnlineUniversities.com‘s blog in their list of the 50 Best Blogs for Education Leaders; it was one of the five blogs listed in the Subject Specific category. What a nice surprise. I’m very honored for the recognition! This is the first I’d read their…
Steven Strogatz writes about the elements of mathematics in the NY Times
Yesterday the mathematician Steven Stragatz wrote the first article in a mulit-part series for the NY Times. In this first article, called From Fish to Infinity, he describes his intent. Crazy as it sounds, over the next several weeks… I’ll be writing about the elements of mathematics, from pre-school to grad school, for anyone out…
How to email all the students in your class with only two clicks of your mouse
[Update: thanks to one of the comments below, I could rename this post “How to email all the students in your class with only one click of your mouse.”] This post has no math in it. But it may be helpful to teachers (and others who regularly email a group of people). I often have…
The relative sizes of the stars and planets
My colleague sent me this link which shows the relative sizes of the planets in our solar system and some of the brightest stars in the sky. Not only does it make the Earth look small, it makes our sun look small. Pretty amazing! Just for fun I decided to create an interactive GeoGebra applet…
Playing the probabilities in Settlers of Catan
One of my favorite board games is Settlers of Catan. I encourage all of you to check it out. It is a great game because it is a combination of luck and strategy and it is different each time you play. I’ve been on a big Settlers kick lately, because I’ve downloaded a version for…
Odds and ends: the 2010 Joint Mathematics Meeting and Euler’s Gem
I’ll be heading to the 2010 Joint Mathematics Meeting in San Francisco next week. In case any of you are interested in meeting up, here are a few of the items on my (busy) schedule. Please introduce yourself; it would be nice to put faces with names. I’m giving a talk on some work with…
David Richeson: Division by Zero 