In this section we will summarize the new Mathematica commands that you've
encountered in this lesson.
RSolve is another of Mathematica's equation solving commands---this one will
solve recurrence relations.
ParametricPlot is a way of describing by curve by specifying the x
and y coordinates using separate functions of the same parameter.
Lists are a way of gluing several values into a single compound value.
Lists are handy, for example, when you'd like a function to return more than
one value, such as a pair of coordinates.