There isn't a listing for his MATH 171 class but I'll leave this here.

TA (Kadar K.) was great, I went to his office hours all the time both to confirm HW answers and talk about other math and ML stuff. Though Prof himself limits his office hours to a 15 minute zoom call. Pretty slow-paced course, lots of time to go off on tangents, tell jokes, and throw shade at the worst students. But that gives Prof time to make absolutely sure everyone understands every concept, which I like. Interesting concepts with many computations and not many super rigorous proofs. He writes hard tests but makes sure the class gets a B+ average, which I also like because it becomes less about being super careful and more about understanding things. No extra credit, but gives reasonable partial credit. You can't drop exams, but you can drop a homework (which the other TA (forgot her name) graded kind of brutally). I also appreciate how I've talked to prof for 15+ minutes after class before and he still tries to help, and also he keeps his email open to students.

Unless you're pretty capable, you'll have to show up to class, but you can be late. He gives you an oral exam if you don't show up to enough randomly selected ends-of-classes (like half of them or less), and you lose 10% on your final (worth 50%) if you do poorly on that, but that bar is set pretty low. That could also end up as a double-punishment since your homework average is then capped at 1.5 times your final exam score. If you can't show up, you could dig through the free textbook or make some friends to try learning everything for the oral and written exams. Unfortunately that's a bit hard when there isn't a Piazza or Discord for the class.

Anyway, that class was fun. I'll miss Prof Yin a lot.

Professor Yin was great. I've had some previous experience with probability, so many of the concepts are familiar, but this class uses a more formal approach with set theory. The professor spends a lot of time on examples, but they are well chosen to develop your ability to think about these kinds of problems. I didn't feel that any of them were repetitive, and they demonstrated important concepts from the course. Many came from very interesting questions as well. There are usually 5-8 questions per homework assignment, and these are usually more difficult or theoretical than the exam questions. The exams and grading are very fair.

Professor Yin is by far, the best professor I have had at UCLA. He is an extremely knowledgeable and clear lecturer. His lectures are extraordinarily engaging, both because he makes sure to explain the intuition behind concepts, to give proofs where he can, as well as to make jokes, share anecdotes, and make the class fun. His teaching style is simply fantastic. Sometimes he'll spend entire classes, or at least huge portions of classes, explaining just one concept, with big font on the chalkboard, to make sure we get it. I repeat - by far, the best professor I've had at UCLA. If you can take a class with him, TAKE IT.