
 1.2 Cartesian Coordinates in the Plane (Site not responding. Last check: 20071107) 
  In cartesian coordinates (or rectangular coordinates), the ``address'' of a point P is given by two real numbers indicating the positions of the perpendicular projections from the point to two fixed, perpendicular, graduated lines, called the axes. 
  If one coordinate is denoted x and the other y, the axes are called the xaxis and the yaxis, and we write P=(x,y). 
  The axes divide the plane into four quadrants: P is in the first quadrant, Q in the second, R in the third, and S in the fourth. 
 www.geom.umn.edu /docs/reference/CRCformulas/node4.html (150 words) 
