Geometry constructions with software plus a sweet Tic-Tac-Toe game

This morning we played a few games of Tic-Tac-Toe with my dd. At one point I saw her do a move that absolutely didn't benefit her. I noted to her where she should have played. She said, "But I want to let you win."

Maybe she was copying my actions (I let her win often). But this was so sweet that I let go about learning strategy and just let her let me win!

But, back to math. If you've never heard about it before, I wish to draw you attention to geometry software.

Yes, there is software for learning geometry - and it's actually a pretty neat way to learn about geometrical constructions. In fact, it can be way better than just using compass and straightedge.

Just check for yourself. Refresh your memory about constructing a circle around a given triangle. After the text there is an interactive JavaSketchPad applet illustrating the construction.

You can move the points that define the initial triangle, and see how the perpendicular bisectors move, but how they always intersect at a point that becomes the center of the circle.

To circumscribe a circle about a triangle

The site has lots more constructions with applets - just follow the links at the bottom.

So... just imagine the learning when students can build this sort of interactive construction with the software.

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