let A be QC-alphabet ; :: thesis: for p, q being Element of CQC-WFF A st p in TAUT A holds
(p => q) => q in TAUT A
let p, q be Element of CQC-WFF A; :: thesis: ( p in TAUT A implies (p => q) => q in TAUT A )
assume A1: p in TAUT A ; :: thesis: (p => q) => q in TAUT A
p => ((p => q) => q) in TAUT A by Th7;
hence (p => q) => q in TAUT A by A1, CQC_THE1:46; :: thesis: verum