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

theorem
  p => r in TAUT(A) & q => r in TAUT(A) implies ( p 'or' q ) => r in TAUT(A)
proof
  assume p => r in TAUT(A) & q => r in TAUT(A);
  then
A1: ( p => r ) '&' ( q => r ) in TAUT(A) by Lm4;
  (( p => r ) '&' ( q => r )) => (( p 'or' q ) => r) in TAUT(A) by Th36;
  hence thesis by A1,CQC_THE1:46;
end;
