let V be RealLinearSpace; :: thesis: for W1, W2 being Subspace of V holds (0). W1 is Subspace of W2
let W1, W2 be Subspace of V; :: thesis: (0). W1 is Subspace of W2
(0). W1 = (0). W2 by Th37;
hence (0). W1 is Subspace of W2 ; :: thesis: verum