<P> For three - dimensional systems, a convention is to portray the xy - plane horizontally, with the z - axis added to represent height (positive up). Furthermore, there is a convention to orient the x-axis toward the viewer, biased either to the right or left . If a diagram (3D projection or 2D perspective drawing) shows the x - and y - axis horizontally and vertically, respectively, then the z - axis should be shown pointing "out of the page" towards the viewer or camera . In such a 2D diagram of a 3D coordinate system, the z - axis would appear as a line or ray pointing down and to the left or down and to the right, depending on the presumed viewer or camera perspective . In any diagram or display, the orientation of the three axes, as a whole, is arbitrary . However, the orientation of the axes relative to each other should always comply with the right - hand rule, unless specifically stated otherwise . All laws of physics and math assume this right - handedness, which ensures consistency . </P> <P> For 3D diagrams, the names "abscissa" and "ordinate" are rarely used for x and y, respectively . When they are, the z - coordinate is sometimes called the applicate . The words abscissa, ordinate and applicate are sometimes used to refer to coordinate axes rather than the coordinate values . </P> <P> The axes of a two - dimensional Cartesian system divide the plane into four infinite regions, called quadrants, each bounded by two half - axes . These are often numbered from 1st to 4th and denoted by Roman numerals: I (where the signs of the two coordinates are +, +), II (−, +), III (−, −), and IV (+, −). When the axes are drawn according to the mathematical custom, the numbering goes counter-clockwise starting from the upper right ("north - east") quadrant . </P> <P> Similarly, a three - dimensional Cartesian system defines a division of space into eight regions or octants, according to the signs of the coordinates of the points . The convention used for naming a specific octant is to list its signs, e.g. (+ + +) or (− + −). The generalization of the quadrant and octant to an arbitrary number of dimensions is the orthant, and a similar naming system applies . </P>

Who is the other one who developed the cartesian plane