let p, q be Element of CQC-WFF ; :: thesis: (p '&' q) => (p 'or' q) in TAUT
( p => (p 'or' q) in TAUT & (p '&' q) => p in TAUT ) by Th3, Th19;
hence (p '&' q) => (p 'or' q) in TAUT by LUKASI_1:3; :: thesis: verum