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
  Sum<*c1,c2,c3*> = c1 + c2 + c3
proof
  thus Sum<*c1,c2,c3*> = Sum<*c1,c2*> + c3 by Th31
    .= c1 + c2 + c3 by Th34;
end;
