English
For every p : Lex α → Prop, (∀ a, p a) is equivalent to (∀ a, p (toLex a)).
Русский
Для каждого p : Lex α → Prop, (∀ a, p a) эквивалентно (∀ a, p (toLex a)).
LaTeX
$$$\forall p:\, Lex\,\alpha \to \mathrm{Prop},\quad (\forall a, p\,a) \iff \forall a, p(\mathrm{toLex}\,a)$$$
Lean4
@[simp]
theorem «forall» {p : Lex α → Prop} : (∀ a, p a) ↔ ∀ a, p (toLex a) :=
Iff.rfl