2K The Cartesian plane and graphs

Learning intentions for this section:

• To know the meaning of the terms Cartesian plane (or number plane), domain, range, origin and coordinates

• To be able to interpret the location of a point described by its coordinates

• To be able to plot points given their coordinates

Past, present and future learning:

• Students may be familiar with the Cartesian plane from Stage 3

• This section prepares students for future work in Linear Relationships in Stage 4 and beyond

We are already familiar with number lines. A number line is used to locate a position in one dimension (i.e. along the line).

A number plane is used to locate a position in two dimensions (i.e. within the plane). A number plane uses two number lines to form a grid system, so that points can be located precisely. A rule can then be illustrated visually using a number plane by forming a graph.

Lesson starter: Estimate your location

Consider the door as ‘the origin’ of your classroom.

• Describe the position you are sitting in within the classroom in reference to the door.

• Can you think of different ways of describing your position? Which is the best way? Submit a copy of your location description to your teacher.

• Can you locate a classmate correctly when location descriptions are read out by your teacher?

Key Ideas

What is the position of this point on the number plane?

■ A number plane is used to represent position in two dimensions, therefore it requires two coordinates.