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Plotting Points and Naming Quadrants - Concept 26,472 views

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

As we learn how to graph, we will need a thorough knowledge of the fundamentals of graphing: plotting points and identifying coordinates. One of the most important things to know is the terminology of what we call the Cartesian coordinate system, or an xy graph. Plotting points will be useful when we start to interpret graphs and graph lines using a table of values.

One of the things you guys will quickly learn about math class if you haven't already is that it's like a whole other language. There's so much vocabulary to keep your head wrapped around. One of the important things to learn about in your early algebra studies is how we talk about what's called the Cartesian Coordinate Plane, which pretty much means a graph. What the story is that this guy who is a French mathematician. His name is Rene Descartes.
Supposedly, he was lying in his bed and then there was this little fly up on the ceiling and he was trying to describe where the fly was going. And so what he did is he used the ceiling tiles. And he would say, OK. He went over two, up one. He's at the point (2, 1), supposedly. I don't know if that's true or not.
But, that's why we call it the Cartesian Coordinate Plane after him. What the coordinate plane looks like is this. It's these rectangular boxes, that actually if it were perfect they'd be squares. We called the rectangular coordinate system, because it's made up of these little squares.
And there are a couple of vocabulary things you want to keep in mind. The first thing is that this center point where the two... It's called axis cross. It's called the origin. And we label it with the coordinates (0, 0). You guys probably already know that the first number represents your X value, your side to side. The second number represents your Y value. That's your up and down.
So, we call this the X axis, the horizontal axis. We call that vertical part the Y axis. And every dot just like the Descartes' fly has two numbers, over two up one would be something that would look like that. Two is the X number. One is the Y number.
So that's important, how you get the points on there. The other thing, and my friends, this is one of like the weirdest things in math is how we name the quadrants. This graph is broken into four pieces. We call them quadrants. And we name them in a counter clockwise method, which to me is kind of confusing.
Here's what it looks like. This we call quadrant one. And you use the Roman numeral one which looks like a capital "I." This is quadrant two, Roman numeral two. Three and quadrant four is "IV." I'm not sure why we use Roman numerals.
But, quadrants are named in a counter clockwise method like this, quadrant one, two, three and four. It's important that you guys keep all of that vocabulary in your brain throughout your entire math careers, not only in algebra, but for now on.
The Cartesian coordinate system with rectangular coordinates, the origin, the X and Y axis', and the naming of the quadrants, one, two, three and four.