let p, q, r be Element of CQC-WFF ; :: thesis: ( p => q is valid implies (p 'or' r) => (q 'or' r) is valid )
assume p => q in TAUT ; :: according to CQC_THE1:def 10 :: thesis: (p 'or' r) => (q 'or' r) is valid
hence (p 'or' r) => (q 'or' r) in TAUT by PROCAL_1:48; :: according to CQC_THE1:def 10 :: thesis: verum