English
Let π1 and π2 be prepartitions of a fixed box I. If their iUnion are equal, then their complements are equal as well.
Русский
Пусть π1 и π2 — предразбиения некоторого фиксированного прямоугольника I. Если их объединение по индексу i совпадает, то их дополнения совпадают.
LaTeX
$$$ \\forall \\pi_1,\\pi_2:\\mathrm{Prepartition}(I),\\ \\pi_1.iUnion = \\pi_2.iUnion \\Rightarrow \\pi_1.\\mathrm{compl} = \\pi_2.\\mathrm{compl}$$$
Lean4
/-- Since the definition of `BoxIntegral.Prepartition.compl` uses `Exists.choose`,
the result depends only on `π.iUnion`. -/
theorem compl_congr {π₁ π₂ : Prepartition I} (h : π₁.iUnion = π₂.iUnion) : π₁.compl = π₂.compl :=
by
dsimp only [compl]
congr 1
rw [h]