A Miraculous Proof (Ptolemy's Theorem)
youtube.comNumberphile's videos are excellent, a lot of people are probably already following their channel. But this one stands out. It's a delight to watch, I can try to convince you, but the best is to give yourself a 3 minutes try, you'll get hooked as well :)
Speaking as someone who has been in one, they are also a joy to make ... Brady is an absolute genius.