Unformatted text preview: D A4ft7 E ~ ~ 22. We draw the relationship graph 91 with the vertices of a Hamiltonian cycleH, K, DR, LR, F R, BI, Ba, B2 around a circle and labeling interior edges a, b, c, d, e, f, g, h as shown on the left. We then draw a new graph, 1{, whose vertices are labeled a, b, c, d, e, f, g, h and an edge indicates that the corresponding edges of 91 cross. H K B2 DR LR a b c d e Bl FR In order to 2color 1{, it is necessary to remove only one of b, f or h. On the left below, we show the graph 1{ " {b} and a 2coloring. On the right, we redraw 91 " {b} as a planar graph by pulling red edges a, f, g outside the circle....
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 Summer '10
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 Graph Theory, Planar graph, plane graph, corresponding edges

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