let p, q, s be ext-real number ; :: 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 Th308; :: thesis: verum