Petr's miracle: Why was it lost for 100 years (Mathologer Masterclass)

Today’s topic is the Petr-Douglas-Neumann theorem. John Harnad told me about this amazing result a couple of weeks ago and I pretty much decided on the spot that this would be the next Mathologer video. I really had a lot of fun bringing this one to life, maybe too much fun :) Very good Wiki page on the Petr–Douglas–Neumann theorem Napoleon's theorem and the PDN theorem at Cut-the-knot Petr's original paper Worth a look for eigenpolygon decomposition and other application within geometry, etc. A fantastic app that does the eigenpolygon decomposition contributed by Steven De Keninck from the Computer Vision Group at the Uni