Cartesian coordinate system
A Cartesian coordinate system, also known as rectangular coordinate system, can be used to plot points and graph lines. 
It is basically, a set of two number lines The horizontal line is called x-axis and the vertical line is called y-axis A good real life example of a vertical number line or y-axis is a thermometer. Notice that it has 4 quadrants. In quadrant I, x and y are positive In quadrant II, x is negative, but y is positive In quadrant III, x and y are negative In quadrant IV, x is positive, but y is negative The center, or intersection of the two axis is equal to (0,0) In this lesson, you will learn to plot points on the cartesian coordinate system. A point is represented by a pair of numbers (x, y) x stands for any value on the x-axis and y stands for any value on the y-axis An example of a point is (1, 5) Let us now plot some points. Locate point (2,3). x = 2 and y = 3 Draw a vertical line at x = 2 and draw a horizontal line at y = 3 Where the two lines meet or intersect, is your point (in red) 
Locate point (-3, 1) Draw a vertical line at x = -3 and draw a horizontal line at y = 1 The intersection of the two lines is your point 
Locate point (-4, -4) Draw a vertical line at x = -4 and draw a horizontal line at y = -4 
Tricky cases are when points are located on the x-axis or the y-axis. Students usually get confused, so study the following two examples carefully Locate point (2,0) Draw a vertical line at x = 2 and draw a horizontal line at y = 0. Notice that when y = 0, your horizontal line is on the x-axis Important point to remember: When y = 0, your point is always located on the x-axis 
Locate point (0, -3) Draw a vertical line at x = 0 and draw a horizontal line at y = -3. Notice that when x = 0, your vertical line is on the x-axis Important point to remember: When x = 0, your point is always located on the y-axis 
Other examples: 
Graphing Cartesian coordinate system Home page 
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