A couple weeks ago I used pythagorean’s theorem to calculate the maximum size of tv my friend could buy to fit in their entertainment center based on the vertical space they had.

Every time I drive I’m mentally running through calculations on where each car around me is going to be based on their current speed, current acceleration/deceleration, and position relative to other vehicles that may cause a change in acceleration/deceleration. Having learned calculus that’s a lot more intuitive and easier to do than if I hadn’t.

I would be a less functional person if I had not learned anything beyond basic arithmetic.