MATH 120A
Differential Geometry
Description: Lecture, three hours; discussion, one hour. Requisites: courses 32B, 33B, 115A, 131A. Course 120A is requisite to 120B. Curves in 3-space, Frenet formulas, surfaces in 3-space, normal curvature, Gaussian curvature, congruence of curves and surfaces, intrinsic geometry of surfaces, isometries, geodesics, Gauss/Bonnet theorem. P/NP or letter grading.
Units: 4.0
Units: 4.0
2 of 2
Most Helpful Review
This was an interesting class. First of all, it is a class for pure math majors, yet they make math for teaching majors take it as well. That being said, Petersen is a great professor. He is clear and concise about explaining the material. It was not Petersen I had a problem with, it was the material. Most math classes I have been able to idly sit by and not study too much until the final...but this one really whipped me into shape. The HW grader was extremely harsh, so most people got between a 5 and a 7 on all homeworks. If you put a good deal of work into the class, it is easily manageable. He gives reviews before each test and recommends which problems you study from the homework before each exam...I'd say from the 10 questions on the final, 3 were on a final review sheet, 2 were from homework, 3 were simple applications from what we'd seen in class, and there were 2 harder questions. If you don't have to take 120a, then do not, by any means, take it. However, if it is required for your major, take it with Petersen. Just prepare for a hard-working quarter.
This was an interesting class. First of all, it is a class for pure math majors, yet they make math for teaching majors take it as well. That being said, Petersen is a great professor. He is clear and concise about explaining the material. It was not Petersen I had a problem with, it was the material. Most math classes I have been able to idly sit by and not study too much until the final...but this one really whipped me into shape. The HW grader was extremely harsh, so most people got between a 5 and a 7 on all homeworks. If you put a good deal of work into the class, it is easily manageable. He gives reviews before each test and recommends which problems you study from the homework before each exam...I'd say from the 10 questions on the final, 3 were on a final review sheet, 2 were from homework, 3 were simple applications from what we'd seen in class, and there were 2 harder questions. If you don't have to take 120a, then do not, by any means, take it. However, if it is required for your major, take it with Petersen. Just prepare for a hard-working quarter.
AD
Most Helpful Review
Fall 2025 - This course deals with some pretty complex subject matter, but Professor Sarkar made it a manageable and pretty enjoyable class. His lecturing style is a little bit all over the place, and I definitely felt a bit lost at times. That said, he is pretty good at explaining things in an intuitive way and draws a lot of pictures on the board to help understand everything. What really helped me figure out this class was reading the textbook, so I'd highly recommend doing that if you want to make it through this class. The textbook by Do Carmo listed on the syllabus is NOT the one that this class is based off of, everything in this class follows the textbook "Elements of Differential Geometry" by Millman and Parker, which Professor Sarkar listed under "Additional Reading." It took me a couple of weeks to figure this out but it really helped once I could read the textbook to get a better understanding of the lectures. The grading scheme was 50% quizzes, 50% final. There were weekly homework assignments, 10 problems each, that were not turned in. Instead, the quiz each week consisted of 1 question from the homework, and your lowest quiz score was dropped. The final was also drawn entirely from the homework (1 question from each of the 9 assignments). There were some pretty tough homework problems, but Professor Sarkar generally chose the easier ones for the quizzes and final. This class is definitely challenging, but I ended up enjoying it quite a bit and I think Professor Sarkar is a good professor to take it with.
Fall 2025 - This course deals with some pretty complex subject matter, but Professor Sarkar made it a manageable and pretty enjoyable class. His lecturing style is a little bit all over the place, and I definitely felt a bit lost at times. That said, he is pretty good at explaining things in an intuitive way and draws a lot of pictures on the board to help understand everything. What really helped me figure out this class was reading the textbook, so I'd highly recommend doing that if you want to make it through this class. The textbook by Do Carmo listed on the syllabus is NOT the one that this class is based off of, everything in this class follows the textbook "Elements of Differential Geometry" by Millman and Parker, which Professor Sarkar listed under "Additional Reading." It took me a couple of weeks to figure this out but it really helped once I could read the textbook to get a better understanding of the lectures. The grading scheme was 50% quizzes, 50% final. There were weekly homework assignments, 10 problems each, that were not turned in. Instead, the quiz each week consisted of 1 question from the homework, and your lowest quiz score was dropped. The final was also drawn entirely from the homework (1 question from each of the 9 assignments). There were some pretty tough homework problems, but Professor Sarkar generally chose the easier ones for the quizzes and final. This class is definitely challenging, but I ended up enjoying it quite a bit and I think Professor Sarkar is a good professor to take it with.
AD
Most Helpful Review
Fall 2024 - It's...okay. As a class, pretty easy: homeworks were not especially time-consuming or difficult, and the exams were all very straightforward. That being said, it doesn't feel like we learned much at all? Most of the course felt like essentially different ways to dress-up a partial derivative, maybe plus a cross product if you're feeling spicy. If you handed an above-average 32A student our formula sheet and gave them our final, they would honestly probably pass. No other major downsides, the lectures were okay (lots of examples, some neat drawings), but I do feel somewhat let down by this course as an elective. This class only talks about curves and 2-manifolds, so do keep that in mind.
Fall 2024 - It's...okay. As a class, pretty easy: homeworks were not especially time-consuming or difficult, and the exams were all very straightforward. That being said, it doesn't feel like we learned much at all? Most of the course felt like essentially different ways to dress-up a partial derivative, maybe plus a cross product if you're feeling spicy. If you handed an above-average 32A student our formula sheet and gave them our final, they would honestly probably pass. No other major downsides, the lectures were okay (lots of examples, some neat drawings), but I do feel somewhat let down by this course as an elective. This class only talks about curves and 2-manifolds, so do keep that in mind.
Most Helpful Review
Spring 2020 - I thought the course material was fairly straightforward, and Prof. Willis certainly helps make it even more so. He's a clear lecturer and he's always willing to take questions during lecture, help out during office hours, and take suggestions from students about the course structure, which was key since Spring 2020 was remote/online. The overall grade is: weekly homework (20%), two midterms (20% each), and the final (40%). Exams were fair, possibly even more so than the homework assignments, each of which always seemed to have one really tough problem. In general, I'd definitely recommend taking 120A with Willis.
Spring 2020 - I thought the course material was fairly straightforward, and Prof. Willis certainly helps make it even more so. He's a clear lecturer and he's always willing to take questions during lecture, help out during office hours, and take suggestions from students about the course structure, which was key since Spring 2020 was remote/online. The overall grade is: weekly homework (20%), two midterms (20% each), and the final (40%). Exams were fair, possibly even more so than the homework assignments, each of which always seemed to have one really tough problem. In general, I'd definitely recommend taking 120A with Willis.
2 of 2
