English
If S1 and S2 are measurable subsets of α, then their intersection is measurable.
Русский
Если A и B — измеримые подмножества α, то их пересечение измеримо.
LaTeX
$$$\mathrm{MeasurableSet}(s_1) \rightarrow \mathrm{MeasurableSet}(s_2) \rightarrow \mathrm{MeasurableSet}(s_1 \cap s_2)$$$
Lean4
@[simp, measurability]
protected theorem inter {s₁ s₂ : Set α} (h₁ : MeasurableSet s₁) (h₂ : MeasurableSet s₂) : MeasurableSet (s₁ ∩ s₂) :=
by
rw [inter_eq_compl_compl_union_compl]
exact (h₁.compl.union h₂.compl).compl