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(<*c*>^F) = c + Sum F
proof
  reconsider s=c as Element of COMPLEX by XCMPLX_0:def 2;
  thus Sum(<*c*>^F) = Sum <*s*> + Sum F by Th32
    .= c + Sum F by FINSOP_1:11;
end;
