reserve x for set,
  p,q,r,s,t,u for ExtReal,
  g for Real,
  a for Element of ExtREAL;

theorem :: BORSUK_5:91
  for b being Real holds ].-infty,b.] /\ ].p,+infty.[ = ].p,b.]
proof
  let b be Real;
A1: b in REAL by XREAL_0:def 1;
  -infty <= p by XXREAL_0:5;
  hence thesis by A1,Th159,XXREAL_0:9;
end;
