Pôs y pedwar lliw: Gwahaniaeth rhwng fersiynau

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Llinell 4:
Termau:
*Mae "map" yn cyfeirio at [[Plân geometraidd|blân dau-ddimensiwn]], wedi'i rannu gan linellau yn nifer o ranbarthau (neu "wledydd").
*Mae "cyfagos" yn golygu bod dwy ranbarth yn rhannu ffin (llinell; cromlin) cyffredin, ond nid mewn cornel, lle mae tair neu fwy o ranbarthau yn cwrdd.<ref name="Gonthier 2008">From {{harvtxt|Gonthier|2008}}: "Definitions: A planar map is a set of pairwise disjoint subsets of the plane, called regions. A simple map is one whose regions are connected open sets. Two regions of a map are adjacent if their respective closures have a common point that is not a corner of the map. A point is a corner of a map if and only if it belongs to the closures of at least three regions. Theorem: The regions of any simple planar map can be colored with only four colors, in such a way that any two adjacent regions have different colors."</ref>
[[File:Map of United States vivid colors shown.png|thumb|chwith|Map pedwar lliw o'r [[UDA]], gan anwybyddu'r llynnoedd a'r môr (gwyn).]]
 
Canlyniad y ddamcaniaeth yw'r datganiad canlynol, syml: "Nid oes fyth angen mwy na 4 lliw i liwio unrhyw fap".<ref name="Gonthier 2008"/>
Canlyniad y ddamcaniaeth yw'r datganiad canlynol, syml: "Nid oes fyth angen mwy na 4 lliw i liwio unrhyw fap".<ref>From {{harvtxt|Gonthier|2008}}: "Definitions: A planar map is a set of pairwise disjoint subsets of the plane, called regions. A simple map is one whose regions are connected open sets. Two regions of a map are adjacent if their respective closures have a common point that is not a corner of the map. A point is a corner of a map if and only if it belongs to the closures of at least three regions. Theorem: The regions of any simple planar map can be colored with only four colors, in such a way that any two adjacent regions have different colors."</ref>
 
==Hanes==