Finding Points in the Plane

We can find every point in the plane using two numbers. These numbers are called coordinates. We write a point's coordinates inside parentheses, separated by a comma, like this: (5, 6). Sometimes coordinates written this way are called an ordered pair.

The first number in an ordered pair is called the x-coordinate. The x-coordinate tells us how far the point is along the x-axis.

The second number is called the y-coordinate. The y-coordinate tells us how far the point is along the y-axis.

Let's try an example.

A fly is sitting in the plane.

Sam knows that the fly is at point (4, 3). What should he do?

Sam starts at the origin. So far, he has not moved along the x-axis or the y-axis, so he is at point (0, 0).

Because he wants to find (4, 3), Sam moves four units along the x-axis.

Next, Sam turns around and shoots his tongue three units. Sam's tongue goes straight up, in the same direction that the y-axis travels.

Sam has found point (4, 3). He eats the fly happily.