
theorem Th18:
  for G being Group for H1, H2 being strict Subgroup of G holds
  the carrier of H1 /\ H2 = carr G.H1 /\ carr G.H2
proof
  let G be Group;
  let H1, H2 be strict Subgroup of G;
  carr G.H1 = the carrier of H1 & carr G.H2 = the carrier of H2 by Def1;
  hence thesis by Th1;
end;
