reserve A for QC-alphabet;
reserve p, q, r, s for Element of CQC-WFF(A);

theorem Th11:
  ( p 'or' p ) => p in TAUT(A)
proof
  ( p 'or' p ) => ( 'not' p => p ) in TAUT(A) &
  ( 'not' p => p ) => p in TAUT(A)
  by Th5,CQC_THE1:42;
  hence thesis by LUKASI_1:3;
end;
