reserve X for ComplexUnitarySpace;
reserve g for Point of X;
reserve seq, seq1, seq2 for sequence of X;
reserve Rseq for Real_Sequence;
reserve Cseq,Cseq1,Cseq2 for Complex_Sequence;
reserve z,z1,z2 for Complex;
reserve r for Real;
reserve k,n,m for Nat;

theorem Th17:
  Sum(seq,1) = seq.0 + seq.1
proof
  thus Sum(seq,1) = Sum(seq,0) + seq.1 by Th16
    .= seq.0 + seq.1 by BHSP_4:def 1;
end;
