let p be Element of CQC-WFF ; :: thesis: (p 'or' p) => p in TAUT
A1: (p 'or' p) => (('not' p) => p) in TAUT by Th5;
(('not' p) => p) => p in TAUT by CQC_THE1:78;
hence (p 'or' p) => p in TAUT by A1, LUKASI_1:3; :: thesis: verum