English
If a < o and o is principal, then for all n, (op a)^[n] a < o.
Русский
Если a < o и o — principal, то для всех n выполняется (op a)^[n] a < o.
LaTeX
$$$$ \forall a,o,\ \operatorname{partialOrder}.\lt a o \wedge \operatorname{Principal}(op)\ o \Rightarrow \forall n:\mathbb{N},\ \operatorname{partialOrder}.lt( (op\ a)^[n]\ a)\ o. $$$$
Lean4
theorem iterate_lt (hao : a < o) (ho : Principal op o) (n : ℕ) : (op a)^[n] a < o := by
induction n with
| zero => rwa [Function.iterate_zero]
| succ n hn =>
rw [Function.iterate_succ']
exact ho hao hn