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

theorem
  (( p 'or' q ) => r ) => (( p => r ) 'or' ( q => r )) in TAUT(A)
proof
  q => ( p 'or' q ) in TAUT(A) & ( q => ( p 'or' q )) => ((( p 'or' q ) => r
  ) => ( q => r )) in TAUT(A) by Th4,LUKASI_1:1;
  then (( p 'or' q ) => r ) => ( q => r ) in TAUT(A) by CQC_THE1:46;
  then 'not' ( p => r ) => ((( p 'or' q ) => r ) => ( q => r )) in TAUT(A) by
LUKASI_1:13;
  then (( p 'or' q ) => r ) => ( 'not' ( p => r ) => ( q => r )) in TAUT(A) by
LUKASI_1:15;
  hence thesis by Lm1;
end;
