
theorem
  for G being nonnegative-weighted WGraph, W1 being Walk of G, W2 being
  Subwalk of W1 holds W2.cost() <= W1.cost()
proof
  let G be nonnegative-weighted WGraph, W1 be Walk of G, W2 be Subwalk of W1;
  (ex ws being Subset of W1.weightSeq() st W2.weightSeq() = Seq ws )& for
i being Element of NAT st i in dom W1.weightSeq() holds 0 <= (W1.weightSeq()).i
  by Th18,Th28;
  hence thesis by Th2;
end;
