The Cartesian coordinate system is named after René Descartes (1596-1650), the noted French mathematician and philosopher, who was among the first to describe its properties. However, historical evidence shows that Pierre de Fermat (1601-1665), also a French mathematician and scholar, did more to develop the Cartesian system than did Descartes.

To best understand the nature of the Cartesian plane, it is desirable to start with the number line. Begin with line L and let L stand for a number axis (see figure 1). On L choose a point, O, and let this point designate the zeropoint or origin. Let the distance to the right of O be considered as positive; to the left as negative. Now choose another point, A, to the right of O on L. Let this point correspond to the number 1. We can use this distance between O and A to...