theorem Th38:
   for f be Series of 1,R holds f = (f*(NBag1))*BagN1
   proof
     let f be Series of 1,R;
     (f*(NBag1))*BagN1 = f*(id(Bags 1)) by Th11,RELAT_1:36 .= f by FUNCT_2:17;
     hence thesis;
   end;
