let r be ext-real number ; for s being real number holds [.r,+infty .[ \ ].s,+infty .[ = [.r,s.]
let s be real number ; [.r,+infty .[ \ ].s,+infty .[ = [.r,s.]
s in REAL
by XREAL_0:def 1;
hence
[.r,+infty .[ \ ].s,+infty .[ = [.r,s.]
by Th196, XXREAL_0:9; verum