
theorem
  for G1 being _Graph, E being set, G2 being reverseEdgeDirections of G1, E
  holds G1 is Cycle-like iff G2 is Cycle-like
proof
  let G1 be _Graph, E be set, G2 be reverseEdgeDirections of G1, E;
  consider F being PGraphMapping of G1, G2 such that
    A1: F = id G1 & F is isomorphism by GLIBPRE0:77;
  thus thesis by A1, Th48;
end;
