“…If both these edges cross edge (u, z), then the same argument as in the previous case applies. If one of these edges crosses (v, z), it must also cross (w, z) to reach any one of 3 , there is an edge of this cycle crossing (u, z), one crossing (v, z), and one crossing (w, z). Again by Lemma 6, neither (u, z), nor (v, z), nor (w, z) can be crossed by any other edge.…”