reserve s for set,
  i,j for Nat,
  c,c1,c2,c3 for Complex,
  F,F1,F2 for complex-valued FinSequence,
  R,R1,R2 for i-element complex-valued FinSequence;

theorem
  Product ((i*j) |->c) = Product (j |-> (Product (i|->c)))
proof
  reconsider c as Element of COMPLEX by XCMPLX_0:def 2;
  Product ((i*j) |->c) = Product (j |-> (Product (i|->c))) by SETWOP_2:27;
  hence thesis;
end;
