Becoming comfortable with the coordinate plane (also known as the Cartesian plane) is essential to success in graphing. Once you understand this mathematical “map” and can work with it comfortably, you will be able to transfer that understanding to any form of graph and graphing analysis that more advanced classes can throw at you!
Below is a coordinate plane. If you are not a big fan of reading, the video below will review everything written. 🙂
From bcms.leesummit.k12.mo.us
The first feature to notice is the scale along each axis and how those axes are labeled. The horizontal axis is also known as the x-axis, and the vertical axis is the y-axis.
The point where these two axes meet is the origin. This is where both x and y values are zero. From this we can understand that the x-axis is negative to the left of the y-axis and positive to the right, just like our number line from earlier. The y-axis is positive above the x-axis and negative below.
You may also notice the green writing indicating quadrant numbers. These go counter clockwise from the top right numbered one through four. These quadrants are usually notated with roman numerals. You can an example of a point, or ordered pair, in each quadrant. There is a consistent trend with negative and positive values and the quadrants in which they are located. In Quadrant I, both x and y values are positive. In Quadrant II, y is positive and x is negative. In Quadrant III both x and y are negative, the opposite of Quadrant I. Finally, Quadrant IV reflects Quadrant II where x is positive and y is negative. Use these quadrant numbers just as you would use a compass when reading a map. The points, or ordered pairs given can give a hint as to which quadrant to find them.
Finally a quick review of graphing points. An ordered pair (or point) is written as (x,y). You travel along the x-axis (left or right) the first value, then up or down the y value. So for the example (3,5), first we walk 3 steps in the positive direction along the x-axis, then we turn in the positive direction and take 5 more steps to arrive at (3,5). In the same respect, to graph (-3, -5) we would travel 3 steps along the negative x-axis and down 5 steps to arrive in Quadrant III, just as we would expect.
As we progress through lesson 4, you will begin to graph multiple coordinates within the same function or relationship to see the trend graphically!
Graphing Ordered Pairs (Khan Academy)
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Graphing Points and Naming Quadrants Practice (Khan Academy)
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