reserve n,m,k,k1,k2 for Nat;
reserve r,r1,r2,s,t,p for Real;
reserve seq,seq1,seq2 for Real_Sequence;
reserve x,y for set;

theorem Th61:
  seq is bounded_below implies (inferior_realsequence seq) = - (
  superior_realsequence(-seq))
proof
  assume seq is bounded_below;
  then (inferior_realsequence seq).n = - (superior_realsequence(-seq)).n by
Th59;
  hence thesis by SEQ_1:10;
end;
