theorem Th100:
  con_class{a} = {{b} : b in con_class a}
proof
  set A = {{b} : b in con_class a};
  thus con_class{a} c= A
  proof
    let x be object;
    assume x in con_class{a};
    then consider B such that
A1: x = B and
A2: {a},B are_conjugated;
    consider b such that
A3: {a} * b = B by A2,Th88;
    a,a * b are_conjugated by Th74; then
A4: a * b in con_class a by Th81;
    B = {a * b} by A3,ThB37;
    hence thesis by A1,A4;
  end;
  let x be object;
  assume x in A;
  then consider b such that
A5: x = {b} and
A6: b in con_class a;
  {b},{a} are_conjugated by A6,Th81,Th92;
  hence thesis by A5;
end;
