**Rectangular or Cartesian coordinate system**

We will begin with the Rectangular or Cartesian coordinate system. It is just the standard axis system that we employ when sketching our graphs. Here is the Cartesian coordinate system along a few points plotted.

The horizontal & vertical axes, usually called the x-axis & the y-axis respectively, divide the coordinate system up into quadrants as illustrated above. In each of the quadrant we have the given signs for x and y.

Quadrant I x > 0 , or x positive y > 0 , or y positive

Quadrant II x < 0 , or x negative y > 0 , or y positive

Quadrant III x < 0 , or x negative y < 0 , or y negative

Quadrant IV x <0 , or x positive y < 0 , or y negative

Each of point in the coordinate system is described by an **ordered pair **of the form ( x, y ) .