let s be real number ; :: thesis: [.s,+infty .[ \ ].s,+infty .[ = {s}
s in REAL by XREAL_0:def 1;
then s < +infty by XXREAL_0:9;
hence [.s,+infty .[ \ ].s,+infty .[ = {s} by Th404; :: thesis: verum