


GraphsOrdered PairsAn ordered pair is simply a pair of elements written in a certain order (order is important). For example, the numbers 5 and 2 can form two ordered pairs: (5,2) and (2,5).
In general, given two numbers x and y, the two ordered pairs (x,y) and (y,x) are different, unless x = y. The number x is called the first component and y the second component of the ordered pair (x,y).
Ordered pairs have many uses. It can be used to represent an object with two distinguishable parts. For example, a complex number x+iy can be represented by the ordered pair (x,y). In an Excel spreadsheet we use a letter and a number to denote a cell on the sheet. On a street map we use the same method to locate a street. Cartesian Coordinate System in 2DOrdered pairs are useful in representing relationships between two sets of data, in the form of a graph. These can then be represented by points on a grid known as the Cartesian Coordinate System in 2D. The following example illustrates how to represent an ordered pair as a point on this grid. Example 1.To plot the point represented by (2,4): More Exercises (opens in another window)
If a point P is represented by (a,b) we call a and b the coordinates of P. In 2D Cartesian Coordinates, the first coordinate in the ordered pair is called the xcoordinate and the second coordinate in the ordered pair is called the ycoordinate. Exercise 1.Enter
the correct coordinates for the points plotted below, AL.
The two axes partition the plane into 4 regions, called
quadrants.
Example 2.Look at the following example to see which quadrants various points are located in. Check the grid below to confirm the solution. << Number Lines  Graphs Index  Cartesian Coordinate System in 3D >>
