Coordinate Plane

The vertical number line is the y-axis. The horizontal number line is the x-axis.

These two axes intersect at their zero points, called the origin.

The plane containing the x-axis and the y-axis is called the coordinate plane.

The x-axis and the y-axis separate the coordinate plane into four regions called quadrants.

An ordered pair defines a point in the coordinate plane. The ordered pair is written as:

 ( x, y ), where x represents the distance along the x-axis of the point, and y represents the distance along the y-axis of the point. Example: ( 4, -3) is a point in Quadrant IV.

A line segment can be defined by two ordered pairs which are its endpoints. Example: (a,b) and (c,d) define two points on the coordinate plane. Connecting these twompoints forms a line segment. The midpoint of a line segment can be represented by using the following formula:

[( a+c)/2 , (b+d)/2]