Here’s my favorite moment from a workshop in Spokane last week:
It’s about the quickest and most concise illustration I can offer of Guershon Harel’s necessity principle. The moment of need is brief, but really hard to miss. It sounds a lot like laughter.
2014 Feb 19. Christine Lenghaus adapts the interaction for naming angles:
I drew a large triangle and then lots of various sized ones inside it and asked the students to pick an acute angle. I asked a student to describe the one they were thinking about and then another student to come up and mark it! This lead to discussion on how best to label so that we both agree on which angle we were talking about. Gold!
There’s an easy way to do this in Geogebra.
Open up blank Geogebra file, viewing only the Geometry window (no Algebra window).
Click the point tool and make a bunch of points like in Dan’s video.
Then there is a small button AA with one A in black and the other in grey. This button shows and hides labels for all points.