The infamous "proof by intimidation" in its natural habitat. Nothing quite like watching a professor quantum leap through ten algebraic steps, declare "it's obvious," and leave you staring into the void like a shocked Pikachu. Meanwhile, your remaining neurons are desperately trying to figure out what dark mathematical sorcery just happened. Pro tip: if a professor says "it's obvious," it's definitely not obvious to anyone except maybe the three people who wrote the textbook.