An atlas is a collection of maps, traditionally bound into book form, but now found in multimedia formats. As well as geographic features and political boundaries, many often feature geopolitical, social, religious and economic statistics.
The first book that could be called an atlas was constructed from the calculations of Claudius Ptolemy, a Greek geographer working in Alexandria circa A.D. 150. The first edition was published in Bologna in 1477 and was illustrated with a set of 27 maps, though scholars say that it is not known whether the printed maps were engraved versions of original maps made by Ptolemy, or whether they were constructed by medieval Greek scholars from Ptolemy's text.
The origin of the term atlas is a common source of misconception, perhaps because two different mythical figures named 'Atlas' are associated with mapmaking. King Atlas, a mythical King of Mauretania, was, according to legend, a wise philosopher, mathematician and astronomer who supposedly made the first celestial globe. However, the more widely known Atlas is a figure from Greek mythology.
In mathematics, the polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by an angle and a distance. The polar coordinate system is especially useful in situations where the relationship between two points is most easily expressed in terms of angles and distance; in the more familiar Cartesian or rectangular coordinate system, such a relationship can only be found through trigonometric formulation.
As the coordinate system is two-dimensional, each point is determined by two polar coordinates: the radial coordinate and the angular coordinate. The radial coordinate (usually denoted as ) denotes the point's distance from a central point known as the pole (equivalent to the origin in the Cartesian system). The angular coordinate (also known as the polar angle or the azimuth angle, and usually denoted by θ or ) denotes the positive or anticlockwise (counterclockwise) angle required to reach the point from the 0° ray or polar axis (which is equivalent to the positive x-axis in the Cartesian coordinate plane).
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