reserve X for non empty UNITSTR;
reserve a, b for Real;
reserve x, y for Point of X;
reserve X for RealUnitarySpace;
reserve x, y, z, u, v for Point of X;
reserve seq, seq1, seq2, seq3 for sequence of X;
reserve  n for Nat;

theorem
  seq = - ( - seq )
proof
  let n be Element of NAT;
  thus (- ( - seq )).n = - (- seq).n by Th44
    .= - ( - seq.n) by Th44
    .= seq.n by RLVECT_1:17;
end;
