Editing Coordinate system (section)

===Number line===
{{Main|Number line}}
{{Anchor|Number line}} <!-- [[Negative distance]] redirects here. I considered the main but this is better. Courtesy note per [[WP:SPECIFICLINK]]. -->
The simplest example of a coordinate system is the identification of points on a [[line (geometry)|line]] with real numbers using the ''[[number line]]''. In this system, an arbitrary point ''O'' (the ''origin'') is chosen on a given line. The coordinate of a point ''P'' is defined as the signed distance from ''O'' to ''P'', where the signed distance is the distance taken as positive or negative depending on which side of the line ''P'' lies. Each point is given a unique coordinate and each real number is the coordinate of a unique point.<ref>{{cite book |last1=Stewart |first1=James B. |last2= Redlin |first2= Lothar |last3=Watson |first3=Saleem |author-link=James Stewart (mathematician) |title=College Algebra |publisher=[[Brooks Cole]] |year=2008 |edition= 5th |pages=13–19 |isbn=978-0-495-56521-5}}</ref>
[[File:Number-line-right-arrow.svg|center|The number line]]