ABSTRACT
Although we claim to be 3-dimensional beings, much of our mathematical lives has been lived in the plane. The set of ordered pairs of real numbers, {(x, y)jx, y are real}, is our favored mathematical hangout (thus far anyway) for many good reasons. A visual representation of the plane is given by the Cartesian (or rectangular) coordinate system, and allows us to picture what we do. The Cartesian coordinate system is illustrated in Figure 1.
Actual physical representations of planes are everywhere, from the sheet of paper on which these words are printed, to the board on which your teacher writes, to the floor beneath your feet.
