let s be real number ; :: thesis: ].s,+infty .] \ ].s,+infty .[ = {+infty }
s in REAL by XREAL_0:def 1;
then s < +infty by XXREAL_0:9;
hence ].s,+infty .] \ ].s,+infty .[ = {+infty } by Th402; :: thesis: verum