theorem Th28:
  for p be Prime, n be Nat, g2 be Element of GF(p) st p > 2 & g2 = 2 mod p
  holds g2 <> 0.GF(p) & g2 |^n <> 0.GF(p)
  proof
    let p be Prime, n be Nat, g2 be Element of GF(p) such that
    A1: p > 2 and
    A2: g2 = 2 mod p;
    A3: g2 <> 0 by A1,A2,NAT_D:63;
    hence g2 <> 0.GF(p) by EC_PF_1:11;
    g2 |^n <> 0 by A3,EC_PF_1:25;
    hence g2 |^n <> 0.GF(p) by EC_PF_1:11;
  end;
