Last time: | Next time: |
I would say that the author is trying to hammer home the notion that average and instanteous velocities are related, and are related to slopes of lines.
At times the instantaneous rate of change is the average rate of change (for example, when you are moving at a constant rate of speed over a stretch of highway).
Finally, the importance of units -- of knowing how to interpret the rates of change.
The most important part of that is part d. Let's take a look at that. In this part, we're really using the derivative to gather some important information.... (Well, "important" if you like baked potatoes, and want them cooked just so!:)