I was originally intimidated by the harsh comments here about Prof. Hempel, but they are not true. (Which I think is partly because she’s also changed since first several quarters here?)
Prof. Hempel gives engaging lectures, though we didn’t get to finish the last part due to UCLA canceling classes. But her notes are neatly arranged and provide you full guidance in the process. She is a ‘magician’ who demonstrates complicated theorems and proofs in a straightforward, clear and sometimes novel way.
She’s also very helpful through the course, and you can tell she has so much passion about the subject.
The homework grading policy has changed since this quarter: if you get 50% more on the homework, she will give you full credit for the homework, which accounts for 10% of the course in total.
The two midterms are, to be honest, a bit hurry for majority of the people, having an average around 70%. But it’s bearable and somehow trivial if you do the homework diligently and have a clear understanding of the subject.
I can’t speak of the final because it’s take home this quarter due to the corona virus situation, but it’s by no means hard given the time limit is not enforced and you have access to everything you want.
Above all, this is my personal experience. If you are considering taking 115A, Prof. Hempel is a good teacher who can lead you through. But I definitely recommend auditing different lectures before you make the decision. Experiences vary for different people.

Professor Hempel is a great teacher, you can really see how she loves mathematics and how excited she is about teaching. She posts her printed lecture notes online so you don't need the book. She also gives study guides before the exams which are a very good reflection of what is going to be on the actual exams. During her office hours she was always very helpful, ready to answer all of your questions.

I would not recommend Hempel for 31A, especially for anyone who did not take AP Calculus in high school.
The class has two midterms and a cumulative final. The first midterm had errors in two questions, one of which made the problem unsolvable. She kind of adjusted our grades, but her main solution was saying that we could have corrected the problem by changing one of the numbers and solved it like that (which almost no one did because of how the problem was written). The second midterm did not have any errors but was also quite difficult. The final was far easier than the midterms. I got an A on the final but the midterms brought me down to a B+. This was after having taken IB Math SL which my teacher taught the same as AP Calc. Hempel does allow cheat sheets on all the tests for equations you need to know.
In lecture, she would often start out concepts by showing the proofs, which took time away from learning how to do example problems. To me, the proofs were irrelevant for this math class because there were no proofs on the exams, and the lack of example problems make it much harder to do the homework and understand the material.
Homework is assigned, but you don't have to turn it in. I highly recommend doing the homework and also additional practice problems.
If you're a total math whiz, this class will probably be easy for you, but it may be challenging even for people who thought they were great at calculus in high school. I would really avoid this professor if you have no background in calculus.

I found Hempel to be a really good professor! Lecture is clear and engaging, and she's always very open to questions and invested in student learning. She provides lecture notes for the class and follows them to a tee, so if you like that style she's definitely for you. Exams are easy if you have mastered the lecture and homework, but given on a time crunch so be prepared to write fast! Overall, I think Nadja did a great job of introducing us to proofs and covering the material for the course, and I hope to have her again as a professor in the future.

Actually I've known her "reputation" since I first came to UCLA, and thanks to that I could get a spot in Math 115A with a late second pass.
But those comments are too harsh, she's at least not bad.
Her lectures are mostly clear and sometimes confusing, there are some examples along with some concepts. And if you loss your track you would just look at the lecture notes after. The lecture note basically tells everything that she would talk in lecture, so preview and review would benefit you a lot.
Homework is easy and straightforward since all of the hard problems are not graded. And according to the syllabus, as long as you get 50% percent, you would receive full mark (it's really easy to get 10 out of 20)
Midterms are 50 minutes and the majority of the class would run out of time. The median is about 25/35. But overall the questions are not hard, even though you could not finish the exam, you could at least make sure that what you've done is correct.
Due to the coronavirus, all final in math department is 24hr (essentially no time limit). The final is not easy and there are one or two hard problems, which worth about 15% of the final. However, there is no time limit so take your time to figure it out.
Generally speaking, she's not bad and it's definitely OK to take her math 115A.

This review is for MATH31A since she is not listed under that category. My first response to anyone taking her class, is don't. I like to believe she is somewhat knowledgeable in this subject but her teachings do not reflect it. Her lectures are confusing, her midterms are not similar to anything she gives. Overall I will most likely fail this course but I want to emphasize that if you are good at teaching yourself, you might be able to pass this class, but don't expect any help from the professor like I falsely did.

This response is for 31A because I don’t see her teaching it on bruinwalk. I took Calculus in highschool and got an easy A so took this class and expected a quick gpa boost. But nothing she teaches correlates to her midterms at all. The midterms average a 50% and don’t have a curve. The tests are ridiculously difficult for the scope of the class while the quizzes are pretty much done as a class misleading you about the test difficulty. Only a freshman and already regretting a lot.

It's honestly difficult to express just how many ways Hempel failed me as a professor. The material in this class is generally less difficult and engaging than that of previous courses, but rather than go above and beyond and explore anything remotely interesting, she struggled just to teach the necessary material and even skipped sections because we were never on schedule. Her lectures were never engaging, and she often made multiple errors in each step of her calculations. I understand that it's easy to make algebraic mistakes, but how can you come to class so unprepared so often. It sometimes felt like the students had to teach her how to do things because she had so little grasp on why her calculations were failing. For these reasons, over half the class never attended lecture, but those who stayed only found her getting consistently sidetracked by random questions to the point that she would either not finish material or rush through it without fully explaining it. Even if her lectures somehow made no mistakes and stayed relatively on time, they were still so poorly organized and boring that it was impossible to get a good grasp on the material from them. Furthermore, from the structure of her exams, it almost felt like she had a tenuous grasp on the content. We studied concepts that involved partial fractions, integration by parts, complex eigenvalues, and many more in the homework, but, in the second midterm, 20% of the test was on the existence theorem, an idea that was not crucial to most of the concepts of unit two and was barely touched on in lecture. This class is filled with students who have made it through extremely difficult math, physics, and chemistry courses in the past, and it was a little insulting how easy the tests were, not to mention it will most likely force the class to be curved down which feels extremely unfair to everyone involved. On the last day of lecture, someone asked if she would post the rest of the lecture online since she was unable to finish it in class, but Nadja just said, "well, if you can't do this.." and shrugged. I don't think she deserves to be a professor here if she's unwilling to make even that slight effort to accommodate her students. I love math, and I have never enjoyed a math class less than this one.

*THIS REVIEW IS FOR MATH 31A* Do NOT take math 31A or any class with this professor!!! Nadja is extremely unorganized and unprepared when she lectures. I have always been decent at math and understand each of the concepts but the tests were extremely unfair. I felt lost and confused and I have a background in calculus from high school so if you have never taken calculus before do NOT take this class with her. The midterms covered multiple topics and we only had 50 minutes to complete it and it was stuff we had never seen before!! The final was 3 hours of extremely complex problems even though she claims she would not give us problems harder than what we saw in the classroom..She also would often times make mistakes in class. I understand everyone is human and teachers make mistakes but she would make multiple mistakes each lesson and say "uh what am I doing.." If she does not know the material the fact of the matter is that she cannot teach it. Every lecture she made mistakes the whole class would start talking about how terrible of a teacher she is. I am appalled at how she is a professor and did not meet a single person in my class who thought she was helpful. Even the TAs thought her class and teaching style was unfair. Often times the lecture was rushed and I was better off skipping and reading the textbook myself. Also she went out of town multiple times and we had a sub who was even worse than her. She also expresses no concern for her students and did not try to help at all.

Nadja was a mediocre professor. Homework wasn't graded, but there were quizzes in discussions that were questions straight off of recommended homework problems. The midterms and finals weren't too difficult, and she has a nice grading scheme that selects the scheme that works most in your favor. ALL THIS BEING SAID, I don't think she actually curved the class? It wasn't a difficult class but no one really got an A? My calculated grade was a 88.something% and it was still a B+?? in a math class???? where the test averages were in the 70% ranges? Its possible everyone did really well and the grading schemes really worked in people's favor, but I was thrown off that this class wasn't the "easy A" everyone said it would be

be warned, it's harder than you think