Here is an animation I created in GeoGebra: As far as I can tell, WordPress only shows you the animation once, when you open this post. You can find the actual .ggb file, and an interactive applet in your browser here. (Links to related transformations applets are on this page.) The idea was to illustrate reflection in… Continue reading User-Controlled GeoGebra Animation

# Tag: Geometry

## Asilomar Report: Conic Sections

As my retirement starts to kick in, I no longer attend conferences — except for one: the annual meeting of the California Math Council (Northern Section.) Once again, I had a great day at Asilomar, a beautiful spot near Monterey, right on the Pacific Ocean. Here is my annual report. Conic Sections Figuring out an approach to… Continue reading Asilomar Report: Conic Sections

## Remembering Lew Douglas

(Post updated on 19 Jan 2020.) The Bay Area Math Project and the Alameda Contra Costa County Math Educators presented Lessons from Lew, a professional development session in memory of Lew Douglas, a leading Bay Area math educator who passed away in April. Lew delighted in math and developed lessons to allow others to share in that wonder. We… Continue reading Remembering Lew Douglas

## Geometry: A Guided Inquiry

In my last post, I discussed Every Minute Counts, a book that influenced me early in my career as a high school teacher in the 1980’s. It was mostly useful because of David R. Johnson’s suggestions on how to run a class discussion, and his insistence that the teacher needs to hear from every student, not just the… Continue reading Geometry: A Guided Inquiry

## In Defense of Geometry: Part II

In my last post, I complained about the shrinkage of geometry, a decades-long trend in US math education. Some of the reasons I suggested for this state of affairs is the offering of a substantial amount of algebra to a much broader population, the growth of calculus as a high school subject, and the increasing place given to… Continue reading In Defense of Geometry: Part II

## In Defense of Geometry: Part I

In 2016, I wrote In Defense of Algebra 2, a blog post addressed to math educators who do not see that Algebra 2 can be engaging and worth teaching to all students. In this post and the next, I defend geometry. This is a different sort of argument. Algebra 2 has been offered to more and… Continue reading In Defense of Geometry: Part I

## April Travels, May Webinar, Summer Workshops

I'll be traveling a lot this month. Here's the plan, should you want to say hello.New York City April 5, 4:30pm: I will present Geometric Puzzles at the Museum of Math Teachers’ Circle. Geometric puzzles are accessible to solvers of all ages, but they can also challenge even the most tenacious of solvers. Join math education author… Continue reading April Travels, May Webinar, Summer Workshops

## Geometric Puzzles at Asilomar

I'll be presenting a session on Geometric Puzzles at the Asilomar meeting of the California Math Council. (Saturday, Dec 2, Sanderling, 1:30pm The printed program says I'm in the middle school, but that is not correct. The app has the location right.). I will include material that I believe is relevant to teachers from kindergarten… Continue reading Geometric Puzzles at Asilomar

## Puzzles for the Classroom

In my last post, I shared some generalities about puzzle creation. Today, I will zero in on the specifics of creating puzzles for the mathematics classroom. I will do this by way of analyzing some examples. Multiple PathsA characteristic of all classrooms is that they are constituted of students whose backgrounds and talents vary widely. … Continue reading Puzzles for the Classroom

## Scissors Congruence!

I attended the San Francisco Math Teachers' Circle last weekend. It was facilitated by Paul Zeitz. The topic: showing two polygons have equal area by cutting one into pieces, and rearranging them to cover the other one with no gaps or overlaps.The assumption was that the area of a rectangle is length times width. The… Continue reading Scissors Congruence!