I was reading the other day about how, at the temple of Delphi, when the holy fire was extinguished, it could not be re-lit by earthly fire. Instead, according to Plutarch, it would be lit using "concave mirrors, of a figure formed by the revolution of an isosceles rectangular triangle." A few days later, inspired by the Greeks (and in imminent danger of falling asleep during a meeting at work), and wondering what was meant by the term "isosceles rectangular triangle," I decided to try to derive the formula for the focus of a parabola. I gave up after muddling into trigonometric identities long since forgotten, and didn't bother looking up the answer. (I did, though, manage to stay awake through the rest of the meeting.) Today, I saw this picture in a NYT story about how students are taking too many AP tests. Hopefully those students will be qualified to be Delphic priests!