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

theorem Th39:
  ( (p => q) '&' p ) => q in IPC-Taut
proof
  set P = p => q;
A1: P => P in IPC-Taut by Th17;
  ( P => P ) => (( P '&' p ) => q ) in IPC-Taut by Th37;
  hence thesis by A1,Def14;
end;
