English
If lift(o.card) < c, and ∀ i, f(i) < c, then bsup(o,f) < c.
Русский
Если lift(o.card) < c и ∀ i, f(i) < c, тогда bsup(o,f) < c.
LaTeX
$$$\\forall o\\,\\forall f:\\, (\\operatorname{lift}(o.card) < c.cof) \\rightarrow (\\forall i, f(i) < c) \\rightarrow \\operatorname{bsup}(o,f) < c.$$$
Lean4
theorem bsup_lt_ord_lift {o : Ordinal} {f : ∀ a < o, Ordinal} {c : Ordinal} (ho : Cardinal.lift.{v, u} o.card < c.cof)
(hf : ∀ i hi, f i hi < c) : bsup.{u, v} o f < c :=
(bsup_le_blsub f).trans_lt (blsub_lt_ord_lift ho hf)