Setting variables to 0 was something I remember doing during Calc 1. Like, with guidance of the teacher/book. Just to see what would happen or reason about it, etc. (Technically doing more limit -> 0 stuff, but functionally the same.)

So kinda funny to do the equivilant of finding my notebook from that class and saying “hm yes, these private notes of a math student dicking around aren’t completely 100% correct. Therefore they must know no math.”

What’s more important is how you interpret all those “Divisions by zero”. Some were valid, but others failed. Sometimes you CAN figure out what n/0 means. Like, even if the actual value is undefined, you can reason “it would be X if it didn’t go off to infinity”. (Think about a graph that gets close to 0 but never reaches it for example. If infinity were a number, then the function would = 0 at that place. Asymptotes if you can recall that concept.) Sometimes it behaves badly and you can’t pick a value it’d get to.

Its neat because the first part of the class is saying we only work with well defined functions with a lot of rules, and then at the end you get to break some of those rules and see why you have them for the basics.

Calc 1 is great btw. Should be a required class (maybe without ALL of the proofs). Sucks 99% of professors make calc 2 a failure pit.

Also super interesting/funny to hear that the English were still so bitter about Leibnitz like 150 years later that they were behind continental math progress. Leibnitz notation stays winning, suck it Newton.