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

theorem :: MEASURE6:37
  [.+infty,p.[ = {}
proof
  not ex x being object st x in [.+infty,p.[
  proof
    given x being object such that
A1: x in [.+infty,p.[;
    reconsider s = x as ExtReal by A1;
A2: +infty <= s by A1,Th3;
    s < p by A1,Th3;
    then p > +infty by A2,XXREAL_0:2;
    hence contradiction by XXREAL_0:3;
  end;
  hence thesis;
end;
