what math do you need to know to solve EFE and understand general relaitivity?
EFE? For general relativity you need differential geometry and courses leading up to it, such as vector analysis, calculus, and differential equations.
Einstein's field theory? Tensor analysis- which is part of the differential geometry mathman mentioned. I would include "partial differential equations" though mathman probably intended to include that in "differential equations".
I meant einstein field equations. Is that all you really need?
On the math front, yes. That's probably several years of college-level math after basic differential and integral calculus.
You also need a solid understanding of classical mechanics and Minkowski 4-vector formulation of special relativity.
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