ABSTRACT
The points in a plane may be placed in one-to-one correspondence with pairs of real numbers. A common method is to use perpendicular lines that are horizontal and vertical and intersect at a point called the origin. These two lines constitute the coordinate axes; the horizontal line is the x-axis and the vertical line is the y-axis. The positive direction of the x-axis is to the right whereas the positive direction of the y-axis is up. If P is a point in the plane one may draw lines through it that are perpendicular to the x- and y-axes (such as the broken lines of Figure 4.1). The lines intersect the x-axis at a 32point with coordinate x 1 and the y-axis at a point with coordinate y 1. We call x 1 the x-coordinate or abscissa and y 1 is termed the y-coordinate or ordinate of the point P. Thus, point P is associated with the pair of real numbers (x 1, y 1) and is denoted P(x 1, y 1). The coordinate axes divide the plane into quadrants I, II, III, and IV. Rectangular coordinates. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203743102/9cca8f32-4688-4a1e-80c2-a6c9068f5153/content/fig4_1.tif"/>
