let r be ExtReal; :: thesis: for s being Real holds ].r,+infty.] \ ].s,+infty.] = ].r,s.]
let s be Real; :: thesis: ].r,+infty.] \ ].s,+infty.] = ].r,s.]
s in REAL by XREAL_0:def 1;
hence ].r,+infty.] \ ].s,+infty.] = ].r,s.] by Th193, XXREAL_0:9; :: thesis: verum