
theorem Th3:
  for V being RealUnitarySpace, W being Subspace of V, w being
  VECTOR of W holds w is VECTOR of V
proof
  let V be RealUnitarySpace;
  let W be Subspace of V;
  let w be VECTOR of W;
  w in V by Th2,RLVECT_1:1;
  hence thesis;
end;
