Trigonometry has been very useful to me in deciding whether I can arrange my 6 panel Japanese screen in an accordion style (folded partially) along a shorter wall. These screens are about 14 feet wide and it is hard to find an appropriate sized wall to display it on. So using, the Pythagorean theorem, i was able to calculate the necessary length of a wall if i were to fold the screen panels in an accordion style. This has helped me in deciding whether to purchase a screen or not. (I have a collection of 15 screens and rotate them according to the seasons like they do in Kyoto).
I don’t use calculus much in my day to day. Algebra, sometimes especially when splitting dinner checks among a mixed group of friends (some friends drink vs. non drinkers).
I was in the math club and participated in the annual math olympiads