Weather map motion. Two-dimensional streamlines based on wind speeds at various levels show areas of convergence and divergence in the wind field, which are helpful in determining the location of features within the wind pattern. A popular type of surface weather map is the surface weather analysis, which plots isobars to depict areas of high pressure and low pressure. Cloud codes are translated into symbols and plotted on these maps along with other meteorological data that are included in synoptic reports sent by professionally trained observers. The use of weather charts in a modern sense began in the middle portion of the
Group of rational points on the unit circle is just "a"/"c" + "ib"/"c", where "i" is the imaginary unit. Conversely, if ("x", "y") is a rational point on the unit circle in the 1st quadrant of the coordinate system (i.e. "x" > 0, "y" > 0), then there exists a primitive right triangle with sides "xc", "yc", "c", with "c" being the least common multiple of "x" and "y" denominators. There is a correspondence between points ("x","y") in the "x"-"y" plane and points "x" + "iy" in the complex plane which will be used below, with ("a", "b") taken as equal to "a" + "ib". The set of