Dear all, I'm searching for a question asked some time ago on mse. It was about the proof of something like the following statement: take a subset S of the unit square of area >1/2. Then S contains the vertices of a right angle triangle. There was a nice answer using integration, though I can't remember who posted it.
I've tried tag search using the mse search box, and a google search, to no avail. Can anyone remember any more about the question?
NB it's possible I have the wrong site, and this was posted on mathoverflow - but I don't think so.