## Doctor Dimension

Twenty-some years ago, I started teaching an advanced high school geometry elective class called Space. I offered it every other year until I retired last year. Most of the course was about transformational geometry and symmetry. (That turned out to be excellent preparation for Common Core geometry. I will be presenting and co-presenting four workshops… Continue reading Doctor Dimension

## Big Fun!

In time for my summer workshops, I have a new page on complex numbers, featuring an explanation of the approach I recommend for teaching this topic, worksheets for Algebra 2 and beyond, and (big fun!) online games to introduce and practice complex number arithmetic.Over the decades, I created versions of these games in three education-oriented… Continue reading Big Fun!

## area of a parallelogram

I posted a GeoGebra animation that suggests the formula for the area of a parallelogram defined by two vectors: <img alt="" height="200" src="data:                                                       <img alt="" height="200" src="data:--Henri

## "Enrichment"

During my first ten years as a teacher, I worked in elementary schools. In addition to team teaching my own class (grade 3, then 4, then 5) I was a math specialist for grades K-5. The basic idea was that there was "normal" math (a lot of arithmetic, textbook-based), and there was "enrichment" math. I… Continue reading "Enrichment"

## Transformational Geometry, cont’d.

As I mentioned in a recent post, I will be one of the presenters at the Bay Area Math Project's summer workshop on Transformational Geometry. As part of preparing for this, I went through my notes, and compiled a sort of syllabus of the relevant lessons from my Space course. Symmetry and transformations are the… Continue reading Transformational Geometry, cont’d.

## Transformational Geometry

One of the features of the Common Core content standards in secondary school is a change in the foundations of geometry. Instead of basing everything on congruence and similarity postulates, as is traditional, the idea is to build  on a basis of geometric transformations: translation, rotation, reflection, and dilation. This is an interesting change, but… Continue reading Transformational Geometry

## Escape! meeting notes 2 — Miras

Notes from the Fall Bay Area meeting of Escape from the Textbook! (continued)back to Part 1 Carlos Cabana challenged us to think of uses for Miras, and for tangrams.Having done a lot with tangrams over the years, I chose to work on Miras. I have a class set of those at school but have not… Continue reading Escape! meeting notes 2 — Miras

## Infinity update

I added a Teachers' Guide to the page on Infinity, an elective course I teach at the Urban School.There is also a fair amount of additional information on the course on edWeb, in the Escape from the Textbook! community. (More info.)--Henri

## Even More Kinesthetic Activities: Distance

(Previous kinesthetic posts: Pascal's Triangle, Graphing)These activities are best done in a gym or playground. Start before discussing circles, perpendicular bisectors, angle bisectors, etc. in a geometry class. It may be best to not do all of the activities in one session.I've done much of this with my own students, but not yet all. I… Continue reading Even More Kinesthetic Activities: Distance

## Kinesthetic intro to Pascal’s Triangle

Question in an online discussion:I'm trying to figure out how to kinesthetically demonstrate Pascal's triangle with my precalculus kidsMy response: I do a lot of kinesthetic activities in geometry and algebra, but haven't yet thought about this particular topic that way.Here's a possibility:- Have students stand in a triangular number arrangement- Give the top student… Continue reading Kinesthetic intro to Pascal’s Triangle