reserve G,G1,G2 for _Graph;
reserve W,W1,W2 for Walk of G;
reserve e,x,y,z for set;
reserve v for Vertex of G;
reserve n,m for Element of NAT;

theorem Th87:
  for n being odd Element of NAT st n <= len W holds W.vertexAt(n)
  in W.vertices()
proof
  let n be odd Element of NAT;
  assume
A1: n <= len W;
  then W.vertexAt(n) = W.n by Def8;
  hence thesis by A1,Lm45;
end;
