Prove:
An edge e of a graph G is a cut-edge if and only if e is not part of any circuit in G.
Proof: Consider that e=(x,y) is a cut edge , Suppose that there is a circuit of cycle (x, P, y, x) containing e. Then if Z = u, Z1, x, y, Z2, v is a walk from u to v using e, u, Z1, P, Z2, v is a walk from u to v that doesn’t use e. Thus e is not a cut edge .
If e is not a cut edge then G−e contains a path P from x to y (x ∼ y in G and relations are maintained after deletion of e). So (y, x, P, y) is a cycle containing e.
6. Prove that the following graphs are connected: (a) The 3 vertex cycle: (b) The following 4 vertex graph: (c) K 7. An edge e of a connected graph G is called a cut edge if the graph G obtained by deleting that edge (V(G) V(G) and E(G) E(G) \<ej) is not connected. Prove that if G1 and G2 are connected simple graphs which are isomorphic and if G1 has a cut edge, then G2 also has a cut edge....
Question 1# (a) Let G be a connected graph and C a non-trivial circuit in G. Prove directly that if an edge e fa, b is removed from C then the subgraph S C G that remains is still connected. "Directly' means using only the definitions of the concepts involved, in this case connected' and 'circuit'. Hint: If z and y are vertices of G connected by path that includes e, is there an alternative path connecting x to y...
(a) Let L be a minimum edge-cut in a connected graph G with at least two vertices. Prove that G − L has exactly two components. (b) Let G an eulerian graph. Prove that λ(G) is even.
Let e be the unique lightest edge in a graph G. Let T be a spanning tree of G such that e /∈ T . Prove using elementary properties of spanning trees (i.e. not the cut property) that T is not a minimum spanning tree of G.
er (a) Let G be a connected graph and C a non-trivial circuit in G. Prove directly that if an edge ={a, b} is removed from then the subgraph S CG that remains is still connected. Directly' means using only the definitions of the concepts involved, in this case 'connected' and 'circuit'. Hint: If r and y are vertices of G connected by path that includes e, is there an alternative path connecting x to y that avoids e? (b)...
3. Given graph G = (V,E), prove that the following statements are equivalent. [Note: the following statements are equivalent definitions of a "tree graph".] 1) There exist exactly one path between any of two vertices u, v EV in the graph G 2) Graph G is connected and does not contain any cycles. 3) Graph G does not contain any cycles, and a cycle is formed if any edge (u, v) E E is added to G 3. Given graph...
A bridge is an edge whose removal disconnects the graph. Prove that any bridge must be in some minimum spanning tree. You may use the cut property in the proof, if you want.
Let G be a graph, and let T, T' be spanning trees in G. Show that if e is an edge in T, then there is an edge e in T' such that the graph obtained by adding the edge e, to T-e is again a spanning tree in G. Let G be a graph, and let T, T' be spanning trees in G. Show that if e is an edge in T, then there is an edge e in...
Prove that, if even degree, then the edge conn G is a nontrivial connected graph in which every vertex has Prove that, if even degree, then the edge conn G is a nontrivial connected graph in which every vertex has
3. Given graph G-(V, E), prove that the following statements are equivalent. [Note: the following statements are equivalent definitions of a "tree graph".] 4) Graph G is connected, but would become disconnected if any edge (u,v) E E is removed from G 5) Graph G is connected and has IV 1 edges 6) Graph G has no cycles and has |V| -1 edges.