Kind of tangentially related (no pun intended), this reminded me of an interesting article by Tom Apostol, well known calculus teacher and textbook author. Here's the opening paragraph:
Calculus is a beautiful subject with a host of
dazzling applications. As a teacher of calculus for
more than 50 years and as an author of a couple of
textbooks on the subject, I was stunned to learn that
many standard problems in calculus can be easily solved
by an innovative visual approach that makes no use of
formulas. Here’s a sample of three such problems:
