Totally agreed here. I understood it only because I literally lived with Euler's identity as a signal processing engineer for many years.. and even I started to

Totally agreed here. I understood it only because I literally lived with Euler's identity as a signal processing engineer for many years.. and even I started to lose him near the end when he was going at 100mph through some of the most crucial steps in the derivation, not necessarily because I didn't understand it, but just because he was going through the tricky steps too quickly. Cool to watch, but not very useful, IMHO.