3 ms·

Thanks for this great link! Richard Feynman, always so pleasant and inspiring.

• throwawaymath 8y ago
  Thanks! I like to collect mathematical "tricks" like this. This was on the /r/math subreddit a couple of days ago and many people were expressing surprise that they'd never encountered it. It seems most people encounter this either as a brief coverage in real analysis or in full emphasis in mathematical physics or quantum field theory courses.