reserve X for set;

theorem Th7:
  for G being Group
  for H being Subgroup of G
  st H is trivial
  holds the multMagma of H = (1).G
proof
  let G be Group;
  let H be Subgroup of G;
  assume H is trivial;
  then the multMagma of H = (1).H by Th6
                         .= (1).G by GROUP_2:63;
  hence thesis;
end;
