Mathematical Blunder #5
Vector products are non-associative. Apparently a neuron misfired as I wrote out the properties for the cross product of two vectors. Fortunately, one student was on their toes and asked, "Are there more properties than are in the textbook?" To be honest, there are but the one of the ones I happened to list was not. Nevertheless, board blunders are gateways to great explorations. I had fun demonstrating the concepts with two long sticks, a stack of dry erase markers and my thumbs.
By the way, to my wife who researched the usefulness of technology in math instruction, that is a key place where technology does improve math instruction. Don't you think a computer visual in 3d would be more effective than my thumbs? It seems like my training in OpenGL (3d computer visualization toolkit) would come in handy just for this.