# Coordinate plane

A coordinate plane, or coordinate system, is used for locating points. When used to locate points on a plane, it is also called a rectangular coordinate system. In a coordinate plane, the x-axis is the horizontal number line, while the y-axis is the vertical one. The origin is the point of intersection of the x-axis and the y-axis, as shown in the figure below.

### Did you know?

There are many other coordinate systems used today. One of these is the global positioning system, a system that allows you to find your location anywhere on Earth at any time, regardless of the weather.

### grid

A grid is a set of uniformly spaced horizontal and vertical line segments.

The x- and y-axes divide the rectangular coordinate system into four sections, or quadrants. They are numbered in order from I to IV (1 to 4), starting in the upper right quadrant and going counterclockwise.

### ordered pair

An ordered pair names a point and tells its location in the coordinate system. An ordered pair is typically written as: (2, 1)

### x-coordinate

The first number in an ordered pair is called the x-coordinate. It indicates a distance along the x-axis, the horizontal axis in the coordinate plane.

### y-coordinate

The second number in the ordered pair is called the y-coordinate

### plotting a point

The following example demonstrates the process of plotting a point given an ordered pair:

Example

To plot the point (4,3), first locate 4 on the x-axis and then 3 on the y-axis, illustrated through the arrows in the figure below. Because both coordinates are positive numbers, the point is located in Quadrant I.

To plot (-4,-3), first locate -4 on the x-axis and -3 on the y-axis, following the arrows shown in the figure above. Because both coordinates are negative numbers, the point is located in Quadrant III.

(-4,3) would be in Quadrant II

(4,-3) would be in Quadrant IV