
Plottings Points in the Cartesian Plane (page 2 of 3) Sections: Introduction to the plane, Plotting points, The four quadrants When you were trying to find your street on that map, you went over to D and then down to 12. And that "D12" designation was unambiguous, because it was easy to tell which stood for which. Even if the designation had been written as "12D", you still would have known which box to go to, because the "D" would still have been across the top and the "12" would still have been along the side. But in the Cartesian plane, both axes are labelled with numbers. How can you tell how far left or right to go, or how far up or down to go? Suppose you were told to
locate "(5,
2)" (pronounced
as "the point five two" or just "five two") on the
plane. Where would you look? To understand the meaning of "(5,
2)", you have
to know the following rule: The xcoordinate
(the number for the xaxis) always comes first. The first number (the first coordinate) is always on the horizontal axis.
Finding the location of (5, 2) and then drawing its dot is called "plotting the point (5, 2)". When plotting, remember that the first number is for the horizontal axis and the second number is for the vertical axis. You always go "so far over or back" and then "so far up or down".
As you can see above, a negative ycoordinate means that you'll be counting down the yaxis, not up.
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