English
For a,b : ∀ i, α(i), the size of Ioo(a,b) equals the product of coordinatewise Icc sizes minus 2: #(Ioo a b) = ∏ i #(Icc(a(i), b(i))) − 2.
Русский
Для функций a,b: ∀ i, α(i) выполняется: |Ioo(a,b)| = (∏ᵢ |Icc(a(i), b(i))|) − 2.
LaTeX
$$$$ \\#(Ioo(a,b)) = \\prod_{i} \\#(Icc(a(i), b(i))) - 2 $$$$
Lean4
theorem card_Ioc : #(Ioc a b) = ∏ i, #(Icc (a i) (b i)) - 1 := by rw [card_Ioc_eq_card_Icc_sub_one, card_Icc]