theorem ThB104:
  for H1,H2 being strict Subgroup of G holds H1,H2 are_conjugated
  implies H2,H1 are_conjugated
proof
  let H1,H2 be strict Subgroup of G;
  given g such that
A1: the addMagma of H1 = H2 * g;
  H2 = H1 * (-g) by A1,ThB62;
  hence thesis;
end;
