let p, q, s be ExtReal; :: thesis: ( p <= q implies ].-infty,q.[ \ [.p,s.] = ].-infty,p.[ \/ ].s,q.[ )
-infty <= s by XXREAL_0:5;
hence ( p <= q implies ].-infty,q.[ \ [.p,s.] = ].-infty,p.[ \/ ].s,q.[ ) by Th309; :: thesis: verum