Periodic Phenomena

In Units 1 and 2, the functions we studied kept growing, kept shrinking, or turned around a few times before heading off toward infinity. Unit 3 is about a completely different kind of behavior: patterns that repeat forever. The height of a bike pedal, the tides, the hours of daylight across a year — each one comes back to where it started, again and again. This note builds the vocabulary we will use for the rest of the unit.