I didn't get into patents until much later.
But I still have one of the maths books that I found extremely useful – An Introduction to the Infinitesimal Calculus by G. W. Caunt (O.U.P. 1914), although my reprint is from 1946. At one time it was known as "Caunt's Bible", it was that good. It has the enormous advantage that it contains innumerable examples, and "practice makes perfect", as the saying goes. It may be over 100 years old, but it's still good today if you need a solid grounding in the basics of both theory and applications.
Chapter 3 is titled Differentiation of Simple Algebraical Functions