GeoGebra Classroom

# Getting to Know the Cartesian Plane

## OBJECTIVE: To learn about the parts of the Cartesian plane

The Cartesian plane (also called coordinate plane or rectangular plane) is a plane region consisting of a horizontal line and a vertical line meeting at right angles (90º) with each other. The horizontal line is called the x-axis, while the vertical line is called the y-axis. All points on the Cartesian plane are identified by an ordered pair of numbers (x, y), also known as coordinates. The first number is called the x-coordinate or abscissa, while the second number is called the y-coordinate or ordinate. The point where the x- and y-axes meet is called the origin and has coordinates (0, 0). The x- and y-axes divide the entire plane into four regions called quadrants. The applet below illustrates the four quadrants.

## THE FOUR QUDRANTS

What property do all the points (x, y) in first quadrant have in common? the second quadrant? the third quadrant? the fourth quadrant? Hint: It has something to do with the signs of the coordinates.

## TRY IT YOURSELF ...

Use the applet below to test your understanding of the rules governing the signs of the coordinates of points on the Cartesian plane. If your answer is correct, a big Correct!!! sign will appear. Otherwise, you'll have to try again.

## TODAY you learned how to identify the parts of the Cartesian plane and how to determine the signs of the coordinates of points on it.

In future lessons, you'll learn how to plot points and lines. ENJOY!