reserve s for set,
  i,j for natural Number,
  k for Nat,
  x,x1,x2,x3 for Real,
  r,r1,r2,r3,r4 for Real,
  F,F1,F2,F3 for real-valued FinSequence,
  R,R1,R2 for Element of i-tuples_on REAL;
reserve z,z1,z2 for Element of COMPLEX;

theorem
  Product ((i*j) |->z) = Product (j |-> (Product (i|->z)))
  proof
    i is Nat & j is Nat by TARSKI:1;
    hence thesis by SETWOP_2:27;
  end;
