Editing Coordinate system (section)

===Polar coordinate system===
{{Main|Polar coordinate system}}
Another common coordinate system for the plane is the ''polar coordinate system''.<ref>{{cite book| last=Finney|first=Ross| author2=George Thomas|author3=Franklin Demana|author4=Bert Waits|title=Calculus: Graphical, Numerical, Algebraic|edition=Single Variable Version|date=June 1994|publisher=Addison-Wesley Publishing Co.|isbn=0-201-55478-X|url-access=registration| url=https://archive.org/details/calculusgraphica00ross}}</ref> A point is chosen as the ''pole'' and a ray from this point is taken as the ''polar axis''. For a given angle ''θ'', there is a single line through the pole whose angle with the polar axis is ''θ'' (measured counterclockwise from the axis to the line). Then there is a unique point on this line whose signed distance from the origin is ''r'' for given number ''r''. For a given pair of coordinates (''r'',&nbsp;''θ'') there is a single point, but any point is represented by many pairs of coordinates. For example, (''r'',&nbsp;''θ''), (''r'',&nbsp;''θ''+2''π'') and (−''r'',&nbsp;''θ''+''π'') are all polar coordinates for the same point. The pole is represented by (0, ''θ'') for any value of ''θ''.
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