2018-11-27: more analysis

I continued thinking about the linear approximation interpretation of differentiability, and looked a bit at Caratheodory’s definition of differentiability.

I worked through the exercises in section 10.1 (basic definitions of differentiation).

I started a page on the chain rule for differentiation. For some reason I’ve always found this result slightly unintuitive, so I wanted to understand it “once and for all”.