>Actually I did ask a question in one class. It was about i, the square root of -1, and that was a hyperspace I couldn't follow. The professor answered that it seems strange but it makes some very interesting proofs possible. That was way too abstract for me. The conceptual mathematicians, they have my admiration.

Ahh, the warm and fuzzy world of complex numbers :).

But then, I was teaching these to high school seniors, and wasn't really pushing it, but then the teaching engineers told me I should have, because these complex numbers come real handy when it comes to calculation of some electrical stuff, as the real part of the number represents the reactance, and the imaginary part the capacitance, and voila the calculation turns out quite simple when done so. Provided you know your complex numbers (and arithmetic with them, and how functions of them behave).

>With this one it's hard to give her advice. She had kept her own counsel for a long time now. I have not given up on it because you never know when she might be taking it in. Sometimes she will ask a followup question days later. She just won't give me the satisfaction of admitting it ;-)
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>I have noticed one interesting thing. It's true of her sister as well. The car is the best place to have good conversations. Maybe it's the boredom of the passing miles.

It's also the problem of walking out at will :)