Appendix B: Coordinate System and Lines There are different coordinate systems. Rectangular (Cartesian) coordinate system Polar coordinate system …… One geometric object can be easily described in one coordinate system but not in another one. That is why there are quite a few coordinate systems out there.

Throughout this course, we only use Cartesian coordinate system: One horizontal line pointing right is called the x-axis One vertical line pointing upward is called the y-axis The intersection point is called the origin, denoted by O These two lines divide the plane into four quadrants

There is a 1–1 correspondence between ordered pairs of real numbers and points on the plane.

P2(x2, y2), denoted by |P1P2|, is given by The distance between two points P1(x1, y1) and P2(x2, y2), denoted by |P1P2|, is given by

Equations of lines