Just like calculus (single as well as multi-variable) and linear algebra are not only useful but really similar to classical mechanics. What are the branches of mathematics that I need to know in order to have that same feeling of deja-vu when studying electricity/magnetism and waves/optics? I remember taking those classes in high school, but I forgot most of it.. I forgot most of mechanics as well, but now that I retook that class in college, focusing primarily on calculus, I feel like I really learned something as opposed to memorising a few of formulas and constants. I know that calculus probably has a lot to do with both waves and electricity, but are there any other additional things I should know? Complex analysis, group theory? Thanks!