Algebra Theater Presents The Tale of the Bad Skier

This is possibly the most unusual of all my slides.

Trig Identities and the Unit Circle

Today in my Pre-Calculus class we were using the Pythagorean Identities

I had an easy way of explaining why the first one was true, a method for explaining the second one with a little more effort, but no good way of getting at the third without an unintuitive tweak. Now I may have found a way [...]

Update on India Merit Pay Study

I recently wrote about a merit pay study in India. One of the authors (Karthik Muralidharan) wrote me an email, wanting to clarify a point:
…as the text of the paper (and table 9) makes clear, there was *NO* difference in test scores between the control and ‘pure control’ schools even though the teachers in the [...]

Math Teacher Shortage?

So, I was at our State Department of Education, getting something tweaked on my teaching certificate. Since teachers have this day off, there was quite a line. We get to talking about what we teach, and I mention I teach high school math.
One of them (an assistant principal) hands me a business card. “We’re looking [...]

Mathematics Books for Non-Mathematicians

Most reviews of “popular” math books I’ve seen tend to be written by mathematicians. That’s understandable, considering they’ll know if the information is accurate; but it doesn’t get the perspective of what it’s like to be in the “target audience” of non-mathematicians.
So for something a little different, I link you to: Adam Cadre’s review of [...]

A Simple Dissection Puzzle

Make only one cut, and then assemble the pieces into a square.
…
This is my new introduction to completing the square. This time around I’m trying to give a strong geometric intuition of what’s going on. I’m hoping to build off of this by excluding the little square, and asking the students how one would figure [...]

On the Ancient Egyptian Value for Pi

Do a little searching on the Internet, and you’ll find the ancient Egyptian value for given as 3.16. Do a little more searching and you might get the more exact answer of .
Where did these numbers come from? How did Egyptians discover the procedure for working with circles in the first place? And finally, did the Egyptians really know anything [...]

Disneyland Causes International Incident

Circa 1959, that is.
You see, Nikita Khrushchev, leader of the Soviet Union, was visiting America. Like many people who visit the US, he wanted to see Disneyland.
The security forces checked it out and even made an alternate itinerary which included a visit, but it was considered too dangerous (possibly from the route to get there, [...]