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# Parallelogram on the coordinate plane

Remember our discussion of the coordinate plane? Sure you do! Let's graph the given coordinates of three of the polygon vertices, and find where the 4th vertex is. Created by Sal Khan.

## Want to join the conversation?

• what would a line with a negative length look like?
• Well a line will always be positive because it's straight with no curves but you can say that the points can be negative so in conclusion it'll just look like any other line
• I dont get . can someone help?
• This is just instructions from the math problem saying that Sal has to make both lines the same length. I hope that's what you were asking for, and if it isn't, please be more specific.
• he found the length of the top line because the top is the same length as the bottom in parallelograms.
• if anyone has a problem remembering horizontal and vertical, here is a simple trick. Horizontal comes from the line in the horizon of the sun, sea, ocean, etc. I hope this helped :)
• It doesn’t
• I've heard that a polygon cannot have curved edges or incomplete sides, so would a circle not be considered a polygon? I mean it is a shape, and all shapes are polygons, right?
• Not all shapes are polygons, and circles have curved sides so they are not polygons.
• If we use the distance formula to solve for this, without knowing that it has to be a parallelogram, than we can get many points that make a polygon ABCD but the polygon is not a parallelogram! Then why does it have to be a parallelogram?
• This problem does not say to use the distance formula. Yes, I know this sounds like the problem is some dictator, but, while we're doing it, it is a dictator of sorts.
• why not just count the units?
• You definitely can just count the units. However, if you're dealing with units that are farther apart....... maybe with distances of 100 or more in between, then counting would become a long and tedious process.
You could also just take the absolute value of the x-coordinates since the y-coordinates are the same to find the distance in between.
Ex. | -1.5 - 4.5 | = | -6 | = 6
• Does anybody else have a problem in using "Drawing polygons with coordinates" For me it is not might user friend. I know the answer but cannot get the hang of plotting it on screen.