reserve GF for add-associative right_zeroed right_complementable Abelian
  associative well-unital distributive non empty doubleLoopStr;
reserve M for Abelian add-associative right_zeroed right_complementable
  vector-distributive scalar-distributive scalar-associative scalar-unital
   non empty ModuleStr over GF;
reserve W,W1,W2,W3 for Subspace of M;
reserve u,u1,u2,v,v1,v2 for Element of M;
reserve X,Y for set, x,y,y1,y2 for object;

theorem
  W1 is Subspace of W3 implies W1 /\ W2 is Subspace of W3
proof
  assume
A1: W1 is Subspace of W3;
  W1 /\ W2 is Subspace of W1 by Th15;
  hence thesis by A1,VECTSP_4:26;
end;
