The coordinate system of a graph is the framework upon which the graph is drawn. A coordinate
system consists of numbered scales that give the base and the direction for measuring points on
the graph. Any point on a graph can be specified by giving its coordinates. Coordinates describe
the location of the point with respect to the scales of the coordinate system. There are several
different coordinate systems commonly encountered.
The Cartesian Coordinate System
The Cartesian Coordinate System, also known as the rectangular coordinate system, consists of
two number scales, called the x-axis (at y = 0) and the y-axis (at x = 0), that are perpendicular
to each other. Each scale is a number line drawn to intersect the other at zero. The zero point
is called the origin. The divisions along the scales may be any size, but each division must be
equal. Figure 1 shows a rectangular coordinate system. The axes divide the coordinate system
into four regions called quadrants. Quadrant I is the region above the x-axis and to the right of
the y-axis. Quadrant II is the region above the x-axis and to the left of the y-axis. Quadrant III
is the region below the x-axis and to the left of the y-axis. Quadrant IV is the region below the
x-axis and to the right of the y-axis.
Figure 1 The Cartesian System