of a point on a grid can be given by a pair of numbers which are
its distances from two lines called the x-axis and the y-axis.
is the point (4,3). The first number 4 is called the x-coordinate.
The second number 3 is called y-coordinate. The coordinates must
be given in the right order. The point (3,4) is at B.
given in this way are called Cartesian after the French mathematician
Rene Descartes 1596-1650.