- A Cartesian Coordinate System identifies each point in
a plane with an ordered pair of real numbers (called the coordinates of
the point) by taking the directed distance of the point from each of two
given perpendicular straight lines (called the axes). Typically one axis
(usually called the x-axis) is placed horizontally with positive direction
to the right, and the other (usually called the y-axis) is placed vertically
with positive direction up. Distance from each axis is measured along the
other one, so the distance from the y-axis is called the x-coordinate and
vice-versa. The coordinates of a point are listed in brackets with the
x-coordinate (also called the Abscissa) first, and the y-coordinate (also
known as the Ordinate) second. The point where the axes meet is called
the Origin and has coordinates (0,0). Points with positive x-coordinate
are in the Right Half Plane and those with negative x-coordinate are in
the Left Half Plane. And similarly positive and negative y-values correspond
to the Upper and Lower Half Planes respectively.

Well that wasn't quite a thousand words, but a picture
would certainly be better!

If you have a Java-enabled browser, then you can use our Graph Explorer to see how the cordinates of a point vary as it is moved about. (Any Computer Algebra System or Graphing Calculator might do as well of course but the specific instructions would be a bit different.)

For guidance through a more detailed exploration you can work through our on-line lab on Cartesian Coordinates.

Here are some more links that you might find useful.

If you have come across any other good web-based illustrations of these and related concepts, please do let us know and we will add them here.

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