theorem Th16:
  seq is convergent implies lim (- seq) = - (lim seq)
proof
  assume seq is convergent;
  then lim ((-1) * seq) = (-1) * (lim seq) by Th15;
  then lim (- seq) = (-1) * (lim seq) by BHSP_1:55;
  hence thesis by RLVECT_1:16;
end;
