Cartesian Coordinate Plane
We draw graphs on a coordinate plane. It is called the Cartesian Coordinate Plane, named after Rene Decartes, who developed these processes. Let’s get to the basics here.
Coordinate Plane: A two-dimension surface. The dimensions are up/down, which we call y, and left/right, which we call x.
Axis: We have two axes (plural of axis).
- The horizontal axis is the x – axis.
- The x – axis is a number line, zero at the center.
- To the left is negative, to the right is positive.
- The vertical axis is the y – axis.
- The y – axis is a number line, zero at the center.
- Down is negative, up is positive.
- The two axes intersect where x = 0 and y = 0. This is a coordinate of (0, 0), called the origin.
- The axes divide the plane into four quadrants. Top right is one, top left is two, bottom left is three and bottom right is four.
Coordinate: A location. In this application, the location is written as an ordered pair. Think of a coordinate as an address, the x number is first, which goes left to right. The y number is second, which goes up and down.
Ordered Pair: A pair of numbers, x and y, written in parenthesis (x, y). x is the input to an equation and y is the output of the equation.
Plotting a Point: To plot a point you start at the origin. You count the distance noted in the x – coordinate of the order pair, then count the distance noted in the y – coordinate of the order pair.