There's a reason there's a somewhat famous joke about a professor who, when asked to explain an step he claimed to be trivial, furrowed his brow deeply, spent t

There's a reason there's a somewhat famous joke about a professor who, when asked to explain an step he claimed to be trivial, furrowed his brow deeply, spent the best part of an hour looking at notes and scribbling on the blackboard only to declare afterwards "Yes! It is trivial!'.