reserve T, X, Y for Subset of MC-wff;
reserve p, q, r, s for Element of MC-wff;

theorem Th48:
  ( p => q ) => (( p '&' s ) => ( s '&' q )) in IPC-Taut
proof
  set P = p => q, Q = p '&' s, S = s '&' q;
A1: P '&' Q => S in IPC-Taut by Th47;
  (( P '&' Q ) => S ) => ( P => ( Q => S )) in IPC-Taut by Th36;
  hence thesis by A1,Def14;
end;
