Does anyone know of a good book on approximations methods? In particular finding approximations to sums, integrals, etc via upper/ lower bounds, power series approximations, etc and bounding the error of the approximation.
This topic has always been a weak point for me. When I'm in some QM or analysis class or something and a professor says "and then of course this is approximately '...'" I usually don't see how they got there without at least a few minutes of effort. Sometimes I still can't figure it out. And it's even harder to find approximations for myself than to just verify that a given approximation works.
Is there some textbook that goes over stuff like this? Whenever I google it I get stuff for computer science algorithms.