Asilomar #2: Geogebra

Session Title

Visualize Algebra & Geometry Concepts With The Greatest Of Ease

Better Title

Geogebra Geogebra & Geogebra Geogebra With The Geogebra Of Geogebra


Bill Lombard, Teacher [site & PowerPoint presentation]


I downloaded Geogebra a million years ago and recognized immediately its value as a free alternative to Geometer’s Sketchpad but I shelved it in my Applications folder and didn’t touch it after that. Like I tweeted during the session, I’m probably the last person in the fifty states to get with this killer program, which lets you create geometric figures, intersect them, drag them, and watch the system change on the fly. This session served one invaluable purpose:

Bill Lombard sat me down for 90 minutes and forced me to play. He demoed the program and I just followed along.

This was a presentation, not a workshop, though, which put Bill Lombard in a difficult position. How do you convey the power of dynamic software when you’re just one guy using it at the front of the Asilomar chapel.

His solution was to ask for audience input and query at every turn.

“What color do you want this line?”

“What shape should we draw next?”

“What would be a good variable for this slope slider?”


It was great. People gasped at various intervals, and I’m 99% sure I heard someone muffle a sob somewhere behind me, the software is just that beautiful.


Combination PowerPoint & software demonstration.


A tri-fold paper (not the only time I saw this format) useful mostly as a link to his personal site.


  • A tall gangly guy walked in late and Lombard called him out in front of the entire crowd, “Hey, Guy! Hey, everybody, this is Guy Foresman.” Lombard continued with an oddly passive-aggressive introduction and the awkwardness of the moment was so overwhelming I seem to have repressed the memory. I vaguely recall Lombard telling everyone that Foresman is trying to turn this awesome, free, open source software into a lame, proprietary, end-user product. Foresman sat down, chagrined. It was like I was six and my parents were fighting.
I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. More here.


  1. I was fortunate enough to hear Markus Hohenwarter present a workshop at FCTM a year ago — he’s the creator of Geogebra. Of course when I went in, I didn’t know that, but it quickly became apparent that this wasn’t just some guy who liked the program and wanted to present it — this was THE guy who wrote it. But since it’s freeware, he wasn’t like most of the commercial presenters who talk in generalities about some issue for the first half of the session, and then spend the second half of the session selling THEIR product/service. He just showed us how it works, and repeatedly said, “I don’t really care if you use it or not” (not in a negative way, just that he wasn’t going to benefit financially whether or not we all decided to use it).

    My particular course load doesn’t lean very much in the geometry direction, so I don’t do much with constructions, etc….. I prefer to use GraphCalc for my Algebra students to play around with changing parameters in the slope-intercept form, etc. Unfortunately, it’s no longer being actively developed but the old version is nicely stable.

  2. Hey,

    I use this program in Calculus and Pre-Calculus courses as wel. It is able to draw graphs that depend on parameters. It calculates derivatives and draws Riemann-sums (with the number of intervals possibly being a parameter).

    It is great to build demonstrations/animations for use in a teacher centred approach. But it exports to interactive webpages, letting you build activities/explorations for pupils with ease.

    I also use it for graph creation for my exams (it is one of the few programs that even exports PSTricks (LaTeX)).

    OK, sorry I’m a Belgian fan.

  3. ….Breaking news……

    I used Geogebra in my Alg. I classes today, and it wasn’t even just so I could write this here! In other words, it was (I feel) a legitimate use. We’re working on point-slope form, and taking an equation in point-slope form and converting it into slope-intercept form, and the associated graphing, etc. What I like about Geogebra (but what GraphCalc can’t do) is that it’ll take input in slope-intercept OR point-slope (or even standard) form.