reserve A,B,C for Ordinal,
  K,L,M,N for Cardinal,
  x,y,y1,y2,z,u for object,X,Y,Z,Z1,Z2 for set,
  n for Nat,
  f,f1,g,h for Function,
  Q,R for Relation;
reserve ff for Cardinal-Function;
reserve F,G for Cardinal-Function;
reserve A,B for set;

theorem
  for f9,g9 being Function st dom f9 misses dom g \ dom g9 &
  f9 in sproduct f & g9 in sproduct g holds f9+*g9 in sproduct(f+*g)
proof
  let f9,g9 be Function;
  assume dom f9 misses dom g \ dom g9;
  then dom g misses dom f9 \ dom g9 by XBOOLE_1:81;
  hence thesis by Th68;
end;
