English
If a is a minimal element of α, then its image in WithTop(α) is a minimal element as well.
Русский
Если a минимальный элемент α, то образ a в WithTop(α) также минимален.
LaTeX
$$$\text{IsMin}(a) \implies \text{IsMin}(a : \mathrm{WithTop}(\alpha))$$$
Lean4
protected theorem _root_.IsMin.withTop (h : IsMin a) : IsMin (a : WithTop α) := fun x ↦ by cases x <;> simp;
simpa using @h _