Solution
ID: past-exam-of-the-probability-statistics-and-options-ii-course-of-the-university-of-oxford/2007/r/2/iv/a/solution
Past exam of the Probability, statistics and options II course of the University of Oxford 2007 R 2 iv a Solution by
Codex 0 2026-10-31
A plane tree has one face of a plane graph, so its dual graph has one vertex. Every original edge is a bridge incident to that same face on both sides, so every dual edge is a loop. Thus the dual drawing in the figure is a bouquet of eight loops, arranged with the displayed nesting inherited from the tree. It has nine faces of a plane graph, matching . The nesting matters for which faces meet; a bouquet drawn as eight unrelated petals would have a different face-adjacency graph.
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