
theorem Th10:
  for V being RealNormSpace,
      x be Point of V,
      y be Point of DualSp V holds
    (-x) .|. y = - x .|. y
proof
  let V be RealNormSpace,
      x be Point of V,
      y be Point of DualSp V;
  thus (-x) .|. y = ((-1)*x) .|. y by RLVECT_1:16
  .= (-1) * x .|. y by Th6
  .= - x .|. y;
end;
