theorem
  (dilation(C)).(v+A) = v+((dilation(C)).A)
  proof
    A1: (dilation(C)).(v+A) = (v+A)(+)C by Def2;
    v + ((dilation(C)).A) = v+(A(+)C) by Def2;
    hence thesis by Th17,A1;
  end;
