let A be QC-alphabet ; :: thesis: for p, q being Element of CQC-WFF A holds (p => q) => (('not' p) 'or' q) in TAUT A
let p, q be Element of CQC-WFF A; :: thesis: (p => q) => (('not' p) 'or' q) in TAUT A
A1: (('not' ('not' p)) => p) => ((p => q) => (('not' ('not' p)) => q)) in TAUT A by LUKASI_1:1;
( ('not' ('not' p)) => q = ('not' p) 'or' q & ('not' ('not' p)) => p in TAUT A ) by Lm1, LUKASI_1:25;
hence (p => q) => (('not' p) 'or' q) in TAUT A by A1, CQC_THE1:46; :: thesis: verum