I’ve been doing more machine learning for work, and I’ve realized a) how much calculus is involved in it and b) how much calculus I had forgotten since I took the courses as an undergraduate almost 30 years ago. I happen to still have my old calculus textbook (I couldn’t sell it back to the bookstore back then), so I dusted it off and started working through all the problems. I’m about halfway through right now, and man I get strange looks from people when I start working calculus problems. Good to know that I’m not alone, although I’m about halfway through the equivalent of 18.01 (1/10th of the poster’s coursework) after 6 months. It doesn’t look like there are that many sample exercises in the online course, though - that may make it harder to really absorb.