let p, q, s be ExtReal; :: thesis: ( p <= s & p < q implies [.p,q.[ \ ].p,s.[ = {p} \/ [.s,q.[ )
[.p,p.] = {p} by Th17;
hence ( p <= s & p < q implies [.p,q.[ \ ].p,s.[ = {p} \/ [.s,q.[ ) by Th298; :: thesis: verum