
theorem RHS3:
  for X be RealUnitarySpace,
      x be Point of X, x1 be Point of RUSp2RNSp X
  st x=x1 holds -x = -x1
proof
  let X be RealUnitarySpace,
      x be Point of X, x1 be Point of RUSp2RNSp X;
  assume AS: x=x1;
  thus -x = (-1) * x by RLVECT_1:16
         .= (-1) * x1 by AS
         .= -x1 by RLVECT_1:16;
end;
