reserve G for _Graph;

theorem Th55:
  for V being set, H being addVertices of G, V
  holds VertexAdjSymRel(H) = VertexAdjSymRel(G)
proof
  let V be set, H be addVertices of G, V;
  VertexDomRel(H) = VertexDomRel(G) by Th25;
  hence thesis;
end;
