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

theorem
  ( p '&' q ) in TAUT(A) implies p in TAUT(A)
proof
  assume
A1: ( p '&' q ) in TAUT(A);
  ( p '&' q ) => p in TAUT(A) by Th19;
  hence thesis by A1,CQC_THE1:46;
end;
