theorem Th42:
  for s being Real, p being Point of TOP-REAL 2 holds
  Arg((Rotate(s)).p) = Arg Rotate(euc2cpx(p),s)
  proof
    let s be Real;
    let p be Point of T2;
    (Rotate(s)).p = cpx2euc(Rotate(euc2cpx(p),s)) by JORDAN24:def 3;
    hence thesis by EUCLID_3:1;
  end;
