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  "body": "\n## Summary\n\nThe line graph $L(G)$ of a [[graph|00C0BR7D7H]] $G$ has the edges of $G$ as its vertices.\nTwo of them are adjacent when they share an endpoint.\nIt turns questions about edges into questions about vertices.\nFor example, a matching of $G$ is an independent set of $L(G)$, and an edge colouring of $G$ is a vertex colouring of $L(G)$.\nThe node [[line graph|CJ57DT86S8]] gives the precise definition.\n\n## Explanations\n\n### L1 human\n\nDraw a dot in the middle of each edge of a graph.\nJoin two of the new dots when their edges meet at a common vertex.\nThe new picture is the line graph.\nFor a star with three arms, the three arms all meet at the centre, so the line graph is a triangle.\n",
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