ABSTRACT
We live in a world that is full of changes and it is to our advantage to keep track of them. Unfortunately, many of them are quite complicated, and it is often practical to approximate the non-linear dependence between variable quantities by the linear ones. This task consists of two parts. First, we need to find an appropriate linear approximation. This is where the derivatives are indispensable. Then, it is important to prove that this approximation is indeed a good one. The limits of functions studied in Chapter 3 are used to accomplish this goal.
