let p, q, s be Element of MC-wff ; :: thesis: (p => q) => (p => (s 'or' q)) in IPC-Taut
A1: (q => (s 'or' q)) => ((p => q) => (p => (s 'or' q))) in IPC-Taut by Th22;
q => (s 'or' q) in IPC-Taut by Def14;
hence (p => q) => (p => (s 'or' q)) in IPC-Taut by A1, Def14; :: thesis: verum