Tuesday, January 24, 2012


...for WordPress, mostly because I'm tired of cutting and pasting Latex into a math blog.  Anyway, to the threes upon threes of regular readers of this blog, here is the new home of Lines and Lines of Tangency: http://linesoftangency.wordpress.com/

See you there?  Yes?  Cool.

Friday, January 20, 2012

The Dead Puppy Theorem

So for the past few months I've been telling my kids that, every time they write (x + y)2 = x2 + y2, they kill a puppy.  In fact, I will hereafter refer to that equation as the Dead Puppy Theorem, or DPT.  Since its discovery in early September, my students' usage of the DPT has accounted for more canine deaths than heartworms. 

Saturday, January 14, 2012


It's going to be a bit of a strange year for Friday the 13ths.  First of all, there will be three of them.  Now that's not especially weird--it happens every few years--but it's the first time since 1984 that they'll be spaced precisely 13 weeks apart.  It's also the last time until 2040 that we'll have three of them in a leap year.  I got all this information from a story on the USA Today website, which featured some words from one Dr. Tom Fernsler of the University of Delaware, a math professor (naturally) who's earned himself the nickname of "Dr. 13."  An interesting tidbit from the good doctor, and bad news for the phobic: the 13th of the month is actually more likely to occur on a Friday than any other day of the week--688 times in a 400-year period.

Wednesday, January 11, 2012

Check, One, Two

Myself and (then) SSgt Clark doing some math in Fallujah, Iraq.

I used to be an artillery officer in the Marine Corps, and it's sometimes fun to bring mathematical details of my former life into the classroom.  Not only is there some useful and interesting math to be found there, but it also buys me the occasional attention of the Call of Duty crowd.  Here is a simple application of Bayes' Theorem to artillery safety.

Tuesday, January 10, 2012


Thanks to the book Group Theory in the Bedroom, by Brian Hayes, I finally found someone to blame for my geometry students' daily growing hatred of mathematical language.  His name is Robert Recorde.  For those of you who, like pre-this-week me, have never heard of Robert Recorde, don't worry: you've seen his handiwork.  Recorde was a 16th-century Welsh doctor, mathematician, and author of Whetstone of Witte (1557), the book in which the modern equals sign first appears.

Sunday, January 8, 2012

The Right Stuf(s)

In my last post we considered the question of whether Double Stuf Oreos actually live up to their name, creme-wise.  Chris Danielson and I have been going back and forth over the use of nutritional info alone to justify crying foul against the National Biscuit Company.  Enough of that.  Let's do some science.

Wednesday, January 4, 2012

What's in a Stuf?

First, New Year's Resolution = more blog posts.  In that spirit...

A few days ago, teacher of math teachers and all-around math dude Christopher Danielson posted an interesting argument with the conclusion that Double Stuf Oreos are not, in fact, stuffed double.  I'll summarize it here.