I hated things like Bessel Functions where we had to do calculations on those huge old mechanical calculators that could multiply and divide to many decimal places but we did it over and over and had to get every one of the many digits put in correctly. They were needed for wave propagation theory. In my case, it wasn't light waves, but electromagnetic waves.
Since slide rules were a critical tool for engineers at the time, we all had good ones. I still have a couple laying around, 59 years old this year, I bought them in the fall of 1961. I still use the triangular architect's scale I bought then, its right here in my desk. When calculators came out, a simple 4 function one cost something like $450. HP was king until TI came out with much less expensive ones that did not use reverse polish. I bought a SR50 instead of a HP35.
Reverse Polish is one of those things that make no damned sense (why in the hell would someone design a calculator to work that way?) unless you understand it's working on a stack. Then it not only makes perfect sense, but if you're clever enough you can do more complex things on it than you could with a "regular" calculator.
I had used plenty of non RPN calculators before entering college, but IN college, an HP41 became my companion. I still have it, but it's broken (there are shops out there that will repair them; it's on my to do list). I've told people that it should be put in my coffin with me.