Measurement and Geometry
Imagine a number line with zero at its centre and negative numbers to the left and positive numbers to the right. You will be accustomed to plotting numbers on such a number line, and demonstrating your understanding of addition, subtraction, multiplication and division using number lines.
The number plane or Cartesian plane is like two number lines that cross at zero; one of them is horizontal and the other is vertical. The Cartesian coordinate system is used to plot points. In the following pages you will see how it is possible to make a connection between number and algebra, and geometry using the Cartesian coordinate system.
The Cartesian plane is named after the French mathematician and philosopher René Descartes (1596–1650), who introduced the coordinate system to show how algebra could be used to solve geometric problems.