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

theorem Th3:
  p => ( p 'or' q ) in TAUT(A)
proof
  p => ( 'not' p => q ) in TAUT(A) by CQC_THE1:43;
  hence thesis by Lm1;
end;
