Cheap Tricks

I keep a roll of wax paper in my office for just such emergencies. Even coming in early today, I wasn't able to force myself to come up with a coherent calculus lesson (How incoherent was calculus class today? Class so was incoherent that I read to them from Woolf's The Waves.), so part way through class we made parabolas out of wax paper. I can not find one good link that explains this. You draw a line (directrix) and a point (focus) and then fold (tangent line) so that the line touches the point (equal distance) and keep folding until you see the parabola.

I love this activity, as it can be adapted to just about any class. The theme (if you can call it that) of class today was "the tangent line doesn't just come from that formula where you multiply by the exponent then reduce it by one."

Now what to do tomorrow?