theorem
  S is (R3) (R11) implies a * (b * (a * b)") <<>> 1.S
  proof
    assume
A1: S is (R3) (R11);
    take (a * b) * (a * b)";
    thus (a * b) * (a * b)" =*=> a * (b * (a * b)") by A1,Th2;
    thus (a * b) * (a * b)" =*=> 1.S by A1,Th2;
  end;
