As promised, here's the solution to the ladder puzzle I posted recently. Ten people sent in correct solutions (congratulations!); some were different from mine, but still based on the same basic ideas, although some used trigonometry. One person even reported being able to solve it mentally, which, as promised, impressed me. I still haven't seen a solution without calculus, but I believe it's possible.

Anyhow, since I'm too lazy to try to get mathematics look good in HTML, here's a PNG from LaTeX: