Henri Picciotto's

Happy New Year!

January 2014

## Recent Blog Posts

Here are links to posts on my Math Education Blog that you might find interesting.
If you are so moved, you may comment on the posts, and/or subscribe to the blog.

### Rich Activities

In 1981, after ten years of teaching math in grades K-5, I became a high school math teacher. It didn't take long for me to realize that in this environment, the opportunity to do "fun math" was much reduced, because of tremendous pressure to "cover", combined with very limited time to do it. However I did not want to give up on the excitement I saw when students were doing so-called "enrichment" lessons in elementary school. Thus started my lifelong quest for rich curricular activities. What do I mean by that? I list my criteria and link to a few examples in this post.

### Connecting the Dots

A square lattice provides an excellent environment for rich activities. It is a microworld that students can explore on dot paper, or on geoboards. What makes it work so well is that it builds on student strengths: it is easier to look at discrete examples and whole numbers than continuous examples and rational or real numbers. If you are familiar with my books Algebra: Themes, Tools, Concepts and Geometry Labs, you know that I've used geoboards to introduce such topics as similarity, slope, area, distance, the Pythagorean theorem, and simplifying radicals. (Both books are free downloads on my Web site. I list the geoboard lessons and labs in this post.)

One particularly beautiful and surprising result in this context is Pick's formula, which gives the area of a geoboard polygon as a function of the number of pegs on its boundary, and the number of interior pegs. This result is can be discovered by students, in an activity which is both challenging and accessible. I link to worksheets on this, and provide a full proof of the formula (for teachers) on a new page in my Web site.

Finally, here are links to posts about two unsolved problems that are suitable for student exploration on the geoboard or dot paper:
No Three on a Line. (This one ties in with slope investigations.)
Heilbronn Triangle (This one connects with exploring geoboard area, or it can be used as an application of Pick's formula.)
I'll present more K-12 unsolved problems in future posts.

### Functions and the Common Core

Functions are a major topic in the Common Core State Standards for math, starting in grade 8. This is quite a departure from traditional curricula, which postpone this topic until Algebra 2, in 10th or 11th grade. There's good and bad in this change.

＊ The good is that the concept of function is certainly accessible to 8th graders, and frankly even to elementary school students. An early introduction makes it easier to put algebra in context through modeling, and in fact can be a tool to teach many other things, including equations, inequalities, and even some important foundational ideas in arithmetic. This is not really a new idea: many curricula developed in the 90's did just that.

One such curriculum is Algebra: Themes, Tools, Concepts, a book I co-authored (more info and links to free download here.) A public school teacher in Utah wrote to me recently that he had been using the book with great success to teach the integrated path CCSSM Math 1. Read his comments here.

＊ The bad is that the authors of the CCSSM decided to introduce function notation too early in the game. Teaching this notation, as well as inverse functions and composition of functions is easy after students have had a couple of years of experience with the basic concept. Doing it in Algebra 1 is unnecessary, and only compounds the problems of that famously ineffective course.

I have a lot more to say on the Common Core. I will be posting my analysis on my Web site after I incorporate feedback from some friends and colleagues. Watch my blog for an announcement when the article becomes available.

### Function Diagrams

Functions are important enough to deserve several representations: graphical, symbolic, numerical, contextual. To that list, I've added the parallel axes representation, or function diagram, a representation which makes many ideas about functions more accessible. For a general overview and many links click here.

Recent posts:
GeoGebra files for function diagrams: here and here
Function diagram applets
Function diagrams at the Asilomar conference and thereafter

### And One More Thing

Two fun talks I attended at Asilomar.

## Bay Area Meeting

If you live in or near San Francisco, join us for a meeting 9am-noon on Saturday, January 11. (Apologies for the late notice.) We will do and discuss a hands-on activity about hyperboloids,

## Summer Workshops

I will offer four workshops this summer (2014), at the
Urban School of San Francisco's Center for Innovative Teaching
June 19-20: Hands-On Geometry (grades 7-10)
June 23-24: Transformational Geometry (grades 8-11)