let V be RealLinearSpace; :: thesis: for W being Subspace of V
for w being VECTOR of W holds w is VECTOR of V
let W be Subspace of V; :: thesis: for w being VECTOR of W holds w is VECTOR of V
let w be VECTOR of W; :: thesis: w is VECTOR of V
w in V by Th17, RLVECT_1:1;
hence w is VECTOR of V by STRUCT_0:def 5; :: thesis: verum