let A be QC-alphabet ; :: thesis: for p, q being Element of CQC-WFF A holds ('not' (p 'or' q)) => ('not' p) in TAUT A
let p, q be Element of CQC-WFF A; :: thesis: ('not' (p 'or' q)) => ('not' p) in TAUT A
( (p => (p 'or' q)) => (('not' (p 'or' q)) => ('not' p)) in TAUT A & p => (p 'or' q) in TAUT A ) by Th3, LUKASI_1:26;
hence ('not' (p 'or' q)) => ('not' p) in TAUT A by CQC_THE1:46; :: thesis: verum