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

theorem Th44:
  ( p => q ) => ((p '&' s) => (q '&' s)) in IPC-Taut
proof
A1: ( (p '&' s) => q ) => ((p '&' s) => (q '&' s)) in IPC-Taut by Th43;
  (p => q) => (( p '&' s ) => q) in IPC-Taut by Th42;
  hence thesis by A1,Th26;
end;
