Rates of Change and Tangent Lines : In this section we will study two fairly important problems in the study of calculus. There are two cause for looking at these problems now.

First one, looking at these problems here will let to begin to understand just what a limit is and what it can tell us regarding a function.

Second one, the rate of change problem which we're going to be looking at is one of the most significant concepts .actually, it's probably one of the most significant concepts that we'll encounter in the whole course.  Hence looking at it now will get us to begin thinking about it from the very beginning.