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

theorem Th330:
  p <= q implies [.-infty,q.] \ ].p,s.] = [.-infty,p.] \/ ].s,q.]
proof
  -infty <= s by XXREAL_0:5;
  hence thesis by Th308;
end;
