theorem Th142:
  Left_Cosets (Omega).G = {the carrier of G} &
  Right_Cosets (Omega).G = {the carrier of G}
proof
  set a = the Element of G;
A1: Left_Cosets (Omega).G c= {the carrier of G}
  proof
    let x be object;
    assume
A2: x in Left_Cosets (Omega).G;
    then reconsider X = x as Subset of G;
    consider a such that
A3: X = a * (Omega).G by A2,Def15;
    a * (Omega).G = the carrier of G by Th111;
    hence thesis by A3,TARSKI:def 1;
  end;
A4: Right_Cosets (Omega).G c= {the carrier of G}
  proof
    let x be object;
    assume
A5: x in Right_Cosets (Omega).G;
    then reconsider X = x as Subset of G;
    consider a such that
A6: X = (Omega).G * a by A5,Def16;
    (Omega).G * a = the carrier of G by Th111;
    hence thesis by A6,TARSKI:def 1;
  end;
  (Omega). G * a = the carrier of G by Th111;
  then the carrier of G in Right_Cosets(Omega).G by Def16;
  then
A7: {the carrier of G} c= Right_Cosets(Omega).G by ZFMISC_1:31;
  a * (Omega).G = the carrier of G by Th111;
  then the carrier of G in Left_Cosets (Omega).G by Def15;
  then {the carrier of G} c= Left_Cosets (Omega).G by ZFMISC_1:31;
  hence thesis by A7,A1,A4;
end;
