I hope you weren't too insulted by the simplicity of my map metaphor for the coordinate plane, but I find it more interesting than the strict mathematical definition. The x portion of the coordinate pair is sometimes called the abscissa, and the y portion is called the ordinate, but that terminology is very old, antiquated, and formal, so you may not hear it unless your teacher is old and antiquated. When writing the coordinate pair, make sure to list the x street first, and then the y street.Įvery point on the coordinate plane is described by a coordinate pair ( x,y). You see, every location in the coordinate plane has an address ( x, y) called a coordinate pair, based on the intersecting street numbers. Written on the door of the bakery is its official coordinate plane address: (-3, 4). For example, let's say I find a great bakery at the intersection of x = -3 and y = 4 streets as shown in Figure 5.2. So, positive vertical streets run through quadrants I and IV, and the negative vertical streets run through quadrants II and III.īecause all of the streets have these handy addresses, it's very simple to pinpoint any location in town. On the other hand, the street immediately to the left of the y-axis has equation x = -1, and the further left you go, the more and more negative the streets get. The y-axis has equation x = 0, and the streets to its right begin with x = 1, and get larger and larger. In a similar way, the vertical streets (all of which have equations " x = something") are numbered as well. Basically, all of the positive horizontal street addresses occur in quadrants I and II, and the negative ones are located in quadrants III and IV.įigure 5.2 You're going to love the fresh-baked bagels in this quadrant II bakery. The first horizontal road below the x-axis has equation y = -1, the next is y = -2, etc. In fact, every one of the horizontal roads in this town has the address " y = something." The first horizontal road above the x-axis in Figure 5.1, for example, has equation (address) y = 1, the road above that has equation y = 2, and so on. The address of the x-axis is the equation y = 0. Just like normal roads, the x- and y-axes also have more official-sounding addresses, in addition to their names. The northeast section of town is quadrant one (I), the northwest is quadrant two (II), the southwest is quadrant three (III), and the southeast is quadrant four (IV). This intersection splits the town into four quadrants, which are numbered in a very specific way. These two roads intersect once, right in the middle of town, at a location called the origin.
In this town, there are only two main roads, one that runs horizontally (called the x-axis) and one that runs vertically (called the y-axis). To best understand the coordinate plane, pretend that it is the map of a small town. The axes split the plane into four quadrants. It is formed by the x-axis and y-axis, which are, respectively, horizontal and vertical lines that meet at a point called the origin. The coordinate plane is a flat grid used to visualize mathematical graphs.