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 Th304; :: thesis: verum