CARTESIAN COORDINATE SYTEM
In math, there is often a need to plot points on a chart or grid. Think about points on a map. To find a particular point, it would be helpful to start in a corner, and then know how far to the right to move, and how far up. In math, we have a system that works like this. It's called the Cartesian Coordinate System, in which we use what are called X and Y coordinates to help identify a point.
Look at the diagram at right. The horizontal line along the bottom is called the X-axis, and the numbers on that line are called X-coordinates. The vertical line at left is called the Y-axis, and the numbers on that line are called Y-coordinates. All of this should bememorized. To identify a point on the grid, we always list the X-coordinate first, followed by the Y-coordinate. We put these coordinates in parentheses, like this: (x, y).
Let's find the coordinates of the points on the grid at right. The square is at (1, 3). We move 1 unit to the right, and then 3 units up. The circle is at (2, 4). The star is at (3, 1), and the triangle is at (5, 2). Note that had there been a point in the very lower left hand corner, its coordinates would have been (0, 0). This is only a very basic introduction to the Cartesian coordinate system. You'll learn much more about it later.
Rene Descartes indeed is correct when he said, "I think, therefore I am."