This one is famous! And super ancient. We aren't sure if old Pythag was the first to come up with it, but if not, he arrived at it independently of anyone prior, and his name is associated with it. It's quite nifty when you really think about it. Take a look! Watch the whole Mathematics playlist: Classical Physics Tutorials: Modern Physics Tutorials: General Chemistry Tutorials: Organic Chemistry Tutorials: Biochemistry Tutorials: Biology Tutorials: EMAIL► ProfessorDaveExplains@ PATREON► Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience! Amazon: Bookshop: Barnes and Noble: Book Depository: