Cartesian coordinate system - Wikipedia, the free encyclopedia

Cartesian coordinate system - Wikipedia, the free encyclopedia: "A Cartesian coordinate system specifies each point uniquely in a plane by a pair of numerical coordinates, which are the signed distances from the point to two fixed perpendicular directed lines, measured in the same unit of length. The coordinates can also be defined as the positions of the perpendicular projections of the point onto the two axes, expressed as a signed distances from the origin."