let p, r, s be ExtReal; :: thesis: ( r <= s implies [.r,+infty.] \ ].p,s.[ = [.r,p.] \/ [.s,+infty.] )
p <= +infty by XXREAL_0:3;
hence ( r <= s implies [.r,+infty.] \ ].p,s.[ = [.r,p.] \/ [.s,+infty.] ) by Th300; :: thesis: verum