
theorem HTh20:
  for V, W being non empty ModuleStr over INT.Ring, f being FrFunctional of V,
  v being Vector of V, w being Vector of W holds
  FrFormFunctional(f,0FrFunctional(W)).(v,w) = 0.INT.Ring
  proof
    let V, W be non empty ModuleStr over INT.Ring;
    let f be FrFunctional of V, v be Vector of V, y be Vector of W;
    set 0F = 0FrFunctional(W), F = FrFormFunctional(f,0F);
    thus F.(v,y) = f.v * 0F.y by HDef10
    .= f.v * 0.INT.Ring by FUNCOP_1:7
    .= 0.INT.Ring;
  end;
