关于block的几个理解 Theorem 5.8 Let R be the relation defined on the edge set of a nontrivial connected graph G by e R f,where e,f eE(G),if e f or e and f lie on a common cycle of G.Then R is an equivalence relation. 用等价关系来描述边之间的关系，到底有何用意？ 问题5：Block的“极大”特性和“等价类”有何关系？ Each subgraph of G induced by the edges in an equivalence class is in fact a block of G.关于block的几个理解 Theorem 5.8 Let R be the relation defined on the edge set of a nontrivial connected graph G by e R f, where e, f ∈E(G), if e = f or e and f lie on a common cycle of G. Then R is an equivalence relation. 用等价关系来描述边之间的关系，到底有何用意？ Each subgraph of G induced by the edges in an equivalence class is in fact a block of G. 问题5：Block的“极大”特性和“等价类”有何关系？