Coordinate Plane

• the coordinate plane or Cartesian plane
• points on the Cartesian Plane
  
• quadrants

Coordinate Plane or Cartesian Plane

The coordinate plane or Cartesian plane is a basic concept for coordinate geometry. It describes a two-dimensional plane in terms of two perpendicular lines or axes: x-axis and y-axis. The x-axis forms a horizontal number line while the y-axis forms a vertical number line. The x-axis and the y-axis meets at the point of origin.

Points on the Cartesian Plane

The position of a point on the Cartesian plane is represented by a pair of numbers. The pair is called an ordered pair or coordinates (x, y). The first number, x, called the x-coordinate and the second number, y, is called the y-coordinate.

The origin is indicated by the ordered pair or coordinates (0, 0)

To get to the point (x, y), we start from the origin.
If x is positive then we move x units right from the origin otherwise if x is negative then we move x units left from the origin. Then, if y is positive, we move y units up otherwise if y is negative, we move y units down. 

In the following coordinate plane: .
Point M has coordinates (2, 1.5). To get to point M, we move 2 units to the right (positive) and 1.5 units up (positive).
Point L is represented by the coordinates (–3, 1.5). To get to point L, we move 3 units to the left (negative) and 1.5 units up (positive)
Point N has coordinates (–2, –3). To get to point N, we move 2 units to the left (negative) and 3 units down (negative).

Quadrants

Notice that the x-axis and y-axis divide the Cartesian plane into 4 regions known as quadrants.  They are labelled 1st, 2nd, 3rd and 4th quadrants accordingly in an anticlockwise direction.

Quadrant 1 contains positive x values and positive y values.
Quadrant 2 contains negative x values and positive y values.
Quadrant 3 contains negative x values and negative y values.
Quadrant 4 contains positive x values and negative y values.

This video introduces the coordinate plane or Cartesian plane, quadrants and how to plot points on the Cartesian plane.

This video shows some examples of how to find the ordered pair or coordinates of a given point and how to plot the point given the ordered pair or coordinates.

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