The document introduces the coordinate plane as a tool for working with equations in two variables. It explains how to create a coordinate plane by drawing perpendicular x and y axes that intersect at the origin, and using the axes to locate points on the plane using ordered pairs of numbers (x,y) as coordinates. It describes how to plot points by starting at the origin and counting along the x-axis and y-axis according to the x and y coordinates of the point. Finally, it divides the coordinate plane into four quadrants.

1. Coordinate Plane May 2010

2. Coordinate Plane In this unit we'll be learning about equations in two variables. A coordinate plane is an important tool for working with these equations. It is formed by a horizontal number line, called the x-axis , and a vertical number line, called the y-axis . The two axes intersect at a point called the origin . You can locate any point on the coordinate plane by an ordered pair of numbers (x,y), called the coordinates. Next Back

3. To create a coordinate plane: Draw a horizontal line. This line is called the x-axis and is used to locate values of x. To show that the axis actually goes on forever in both directions, use small arrowheads at each end of the line. Mark off a number line with zero in the center, positive numbers to the right, and negative numbers. Coordinate Plane Back Next

4. To create a coordinate plane: Coordinate Plane 2. Next draw a vertical line that intersects the x axis at zero. This line is called the y-axis and is used to locate the values of y. Mark off a number line with zero in the center, positive numbers going upwards, and negative numbers going downwards . Back Next

5. Coordinate Plane Back Next

6. Locating Points Using Ordered Pairs We can locate any point on the coordinate plane using an ordered pair of numbers like the example shown here, the ordered pair 3 and 1 (point P). We call the ordered pair the coordinates of the point. The coordinates of a point are called an ordered pair because the order of the two numbers is important. Back Next

7. Locating Points Using Ordered Pairs - The first number in the ordered pair is the x coordinate. - The second number in the ordered pair is the y coordinate . Back Next

8. - To plot a point, start at the origin and count along the x axis until you reach the x coordinate, count right for positive numbers, left for negative. - Then count up or down the number of the y coordinate (up for positive, down for negative.) Locating Points Using Ordered Pairs Back Next

9. To make it easy to talk about where on the coordinate plane a point is, we divide the coordinate plane into four sections called quadrants. Quadrants (+, +) (+, -) (-, +) (-, -) Back Next

10. Example Back Next

11. Answer Back