let seq be ExtREAL_sequence; ( seq is bounded & seq is non-increasing implies ( seq is convergent_to_finite_number & seq is convergent & lim seq = inf seq ) )
assume that
A1:
seq is bounded
and
A2:
seq is non-increasing
; ( seq is convergent_to_finite_number & seq is convergent & lim seq = inf seq )
reconsider rseq = seq as Real_Sequence by A1, Th11;
A3:
seq is bounded_below
by A1, Def5;
then A4:
rseq is bounded_below
by Th13;
then
lim rseq = lim_sup rseq
by A2, RINFSUP1:89;
then
lim rseq = lower_bound rseq
by A2, RINFSUP1:70;
then A5:
lim seq = lower_bound rseq
by A2, A4, Th14;
rng seq is bounded_below
by A3, Def3;
hence
( seq is convergent_to_finite_number & seq is convergent & lim seq = inf seq )
by A2, A4, A5, Th3, Th14; verum