The Cartesian Plane - Cycle 3

| Mathematics

What is a Cartesian Plane?

Definition

The Cartesian plane is a reference system.

Example:

Example of a 4-quadrant Cartesian plane.

The Cartesian plane is divided into 4 quadrants separated by the x-axis (horizontal axis) and the y-axis (vertical axis).

Example
The 4 quadrants of a Cartesian plane

Each axis is graduated with positive integers and negative integers. The centre point of the plane is 0.

Example
The positive integers and the negative integers

What are Coordinates?

Definition

Coordinates are numbers that specify the horizontal or vertical position of a point on the Cartesian plane.

The horizontal coordinate represents the position of a point on the x-axis (horizontal axis).
The vertical coordinate represents its position on the y-axis (vertical axis).

Example

The horizontal coordinate of the point is -3.
The vertical coordinate of the point is 1.

Example of a point on a Cartesian plane.

Important!

While the one-quadrant Cartesian plane has only positive coordinates, the Cartesian plane with 4 quadrants has both positive and negative coordinates.

Each quadrant has different positive and/or negative coordinates.

  • 1st quadrant: positive horizontal coordinate, positive vertical coordinate.
  • 2nd quadrant: negative horizontal coordinate, positive vertical coordinate.
  • 3rd quadrant: negative horizontal coordinate, negative vertical coordinate.
  • 4th quadrant: positive horizontal coordinate, negative vertical coordinate.

Examples :

Examples of points on the Cartesian plane.

What is an Ordered Pair?

An ordered pair is used to find the exact position of a point on a Cartesian plane. Write the horizontal coordinate followed by the vertical coordinate between brackets. Separate the two coordinates by a comma.

Example
Example of ordered pair

What is the Origin?

Definition

The origin is the meeting point (the intersection) of the x-axis (horizontal axis) and the y-axis (vertical axis). It is represented by the coordinates (0, 0).

Example:

The origin on a Cartesian plane.

How Do You Place a Point on the Cartesian Plane Using its Coordinates?

Rule

To place a point on the Cartesian plane using its coordinates, follow these steps:

  1. Look at the first coordinate in the ordered pair and find the line corresponding to this number on the horizontal axis.
  2. Look at the second coordinate in the ordered pair and find the line corresponding to this number on the vertical axis.
  3. Place the point where these two lines meet (intersect).
Example

Place the point with coordinates (4, -3) on the Cartesian plane.

  1. Look at the first coordinate in the ordered pair and find the line corresponding to this number on the horizontal axis.

    In the ordered pair (4, -3), the first coordinate is 4.

Example of a Cartesian plane.
  1. Look at the second coordinate in the ordered pair and find the line corresponding to this number on the vertical axis.

    In the ordered pair (4, -3), the second coordinate is -3.

Example of a Cartesian plane.
  1. Place the point where the two lines meet (intersect).
Example of a Cartesian plane.
Example

Place the point with coordinates (-1, -4) on the Cartesian plane.

  1. Look at the first coordinate in the ordered pair and find the line corresponding to this number on the horizontal axis.

    In the ordered pair (-1, -4), the first coordinate is -1.

Example of a Cartesian plane.
  1. Look at the second coordinate in the ordered pair and find the line corresponding to this number on the vertical axis.

    In the ordered pair (-1, -4), the second coordinate is -4.

Example of a Cartesian plane.
  1. Place the point where the two lines meet (intersect).
Example of a Cartesian plane.

How to Find the Position of a Point on the Cartesian Plane?

Rule

To find the position of a point on the Cartesian plane, follow these steps:

  1. Find the horizontal coordinate of the point.
  2. Find the vertical coordinate of the point.
  3. Write the ordered pair with the horizontal coordinate followed by the vertical coordinate in brackets, and separate them by a comma.
Example

Write the position of the point on the following Cartesian plane.

Example of a point on a Cartesian plane.

  1. Find the horizontal coordinate of the point.

    The point is on the line corresponding to -2 on the horizontal axis.

Example of a Cartesian plane.
  1. Find the vertical coordinate of the point.

    The point is on the line corresponding to -1 on the vertical axis.

Example of a Cartesian plane.
  1. Write the ordered pair with the horizontal coordinate followed by the vertical coordinate in brackets, and separate them by a comma.
(-2, -1)
Example

Write the position of the point on the following Cartesian plane.

Example of a point on a Cartesian plane.

  1. Find the horizontal coordinate of the point.

    The point is on the line corresponding to 5 on the horizontal axis.

Example of a Cartesian plane.
  1. Find the vertical coordinate of the point.

    The point is on the line corresponding to -5 on the vertical axis.

Example of a Cartesian plane.
  1. Write the ordered pair with the horizontal coordinate followed by the vertical coordinate in brackets, and separate them by a comma.

(5, -5)