I did not enjoy this class because I suck at calculus, but Li was a good professor. He seemed to be concerned with our success and was open to our feedback as a relatively new professor. Lectures and discussion didn't require attendance. There were 2 midterms, a final, and 3 quizzes (in discussion section). Discussion sections usually just involved practice problems. The quizzes were pretty easy (I had a good TA who helped us prepare for every quiz) and the exams were tough, but I think if you study a lot you can do well (I'd recommend doing just a lot of practice problems). For all of the exams, Li gave us a few formulas, but you weren't allowed to have a cheat sheet, so memorizing all of the formulas and theorems is tough. Lectures weren't posted anywhere, but you could get that week's notes from him every Friday after class. Overall, not a horrible class, and Li is a decent and fair professor.

Easy class mid professor.

My experience with this class is that if you do the homework problems yourself and truly understand each one, you will be able to ace his exams. The midterms are not too bad, you just really need to be able to understand patterns and applying what you learn. The final was more like a huge unit test which did not focus on anything which was before midterm 2. There is a lot of partial credit given so even if you got the wrong answer on a problem, the amount of work you showed adds up and helps you gain some points. Overall, I think the class is extremely doable as long as you are willing to put in the effort.

Overall I liked 31B taught by Professor Li but I wouldn't say this is an easy class.
Good things about this class:
1. The professor is very helpful, he replies to your emails in a timely manner and is often willing to stay after class to answer your questions.
2. Workload is manageable, he gives less work during Thanksgiving break/midterm week.
3. Professor Li is genuinely a nice and chill person.
But there were things that went not so well:
1. Classes are not recorded or broadcasted.
2. Midterms were hard but the Professor was generous with partial credit.
3. The professor's teaching could've been clearer.

Get ready for lots of proofs. Math 131 is essentially all your math classes up to calculus conceptualized into an abstract concept. In other words, you learn how these ideas you've learned in your past math classes come to be (i.e limits, continuity, derivatives). This class is very tricky, requiring you to think outside the box to solve these problems rather than brutal computations. You won't be faced with as much concepts compared to other math classes but with the ideas you learn, you have to apply them to its limit. There are 9 homeworks (one dropped), two midterms and one final in this class where one midterm can be dropped.
Pros:
- Professor is very helpful. He'll answer any questions in a concise way, making sure students understand what he meant. He's even more helpful in office hours as he goes over homework and past exam questions. Highly recommend going to his office hours as that's how I got my homework done.
- Professor is very consistent with lectures. He goes over proofs well (which is rare in the math department) and even if he doesn't have time to do a proof, he lays out the structure in a way we can understand.
Cons:
- Homework is tough af. Every assignment feels like one of those "think outside the box" puzzle games where you have to pull some technique only 200 iq people would think of. This is why his OFFICE HOURS are HELPFUL!
- Exams are just as difficult. His practice exams give you what concepts to expect on each exam but again, you have to think outside the box for each of these questions that you can't really do much to prepare except to do many practice problems.
- Grading is strict, but it could've been because our T.A was a picky grader.

I thought my high school BC teacher was bad but this guy is even worse. He often does 20% of a problem then makes you do the rest on your own time. Professor Li also doesn't post his notes online or record his lectures, instead airdropping them at the end of each week so you better come to every lecture. His quizzes are very easy but the midterms he has given us have had some weird problems he hasn't really taught us how to solve (especially midterm 2). Professor Li occasionally earrapes the class as he isn't that good with the mic. I'm somewhat getting by in his class, but if you're coming from Calc AB or Math 31A/Calc I, good luck.

Professor Li is a great professor teaching-wise; he uses examples that are clear and his teaching style is really nice (he screenshares his iPad as he takes notes on it), and he posts his notes online if you miss class for whatever reason. However, this class is generally difficult and personally for me (someone who struggles with math), it took an insane amount of effort. I did ok on the first midterm (B+), did extremely well on the second (A+), and completely bombed the final (got a F). There are quizzes in discussion on Weeks 3, 6, and 9; and midterms on Weeks 4 and 8, so it feels like there's a test almost every other week. While the quizzes were manageable, it felt like the final was incredibly difficult and nothing like the practice problems. (I also can't tell if the problem lies with me or the test). However, Li is a great professor and I recommend taking the class with him! I enjoyed his class and felt motivated to attend; I just suck at math unless I make it my sole focus and concentration and ignore my other classes 😫

If I'm going to be completely honest, I've never struggled in a class like I️ did in 31B with Li. I️ took AP Calc AB in hs so I️ passed 31A with flying colors the quarter before. Unfortunately, this class hit me like a TRUCK. Professor Li is a new teacher so I️ want to offer understanding, but it's pretty obvious that he isn't skilled in teaching a 300 person class. Li's accent can be a bit hard to understand, and he often explained things in ways that made sense for his brain but not the class as a whole. He doesn't record lectures either which makes attendance extremely important - even though it's so hard to follow along at the speed he teaches/writes. Li isn't necessarily a bad teacher, but I️ wouldn't recommend taking 31B with him unless you've taken BC and know all the material already.