
theorem
  for V being RealUnitarySpace, W1,W2 being Subspace of V holds 0.W1 = 0.W2
proof
  let V be RealUnitarySpace;
  let W1,W2 being Subspace of V;
  0.W1 = 0.V by Def1;
  hence thesis by Def1;
end;
