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
  <*c1*> + <*c2*> = <*c1+c2*>
proof
  reconsider s1=c1, s2=c2 as Element of COMPLEX by XCMPLX_0:def 2;
  <*s1*> + <*s2*> = <*addcomplex.(s1,s2)*> by FINSEQ_2:74
    .= <*c1+c2*> by BINOP_2:def 3;
  hence thesis;
end;
