reserve G for Graph,
  v, v1, v2 for Vertex of G,
  c for Chain of G,
  p, p1, p2 for Path of G,
  vs, vs1, vs2 for FinSequence of the carrier of G,
  e, X for set,
  n, m for Nat;

theorem Th7:
  c = {} implies c is cyclic
proof
  set v = the Vertex of G;
  assume c = {};
  then
A1: <*v*> is_vertex_seq_of c by GRAPH_2:32;
  <*v*>.1 = <*v*>.len <*v*> by FINSEQ_1:40;
  hence thesis by A1;
end;
