mbstone writes: You know those big, electromechanical displays that used to grace railroad stations and airports, the ones with the letters that would flip around and around until the correct message appeared? Sadly, none remain in service, but Cary Dunn has done it in ActionScript — how cool is that? — and I bet his emulation makes its way into real airports real soon now.
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"