If lim(h→0) [tan(π/4 + h) - 1]/h represents f'(a) for some function f at some point a, what are f and a?

Core Concept

The limit definition f'(a) = lim(h→0) [f(a+h) - f(a)]/h matches the given expression when f(a+h) = tan(π/4 + h) and f(a) = tan(π/4) = 1. This identifies f(x) = tan(x) and a = π/4.