English
For all b, n, m: bit b (n + m) = bit b n + bit false m.
Русский
Для всех b, n, m: bit b (n + m) = bit b n + bit false m.
LaTeX
$$$$ \forall (b : \mathrm{Bool}) (n,m : \mathbb{N}), \; \mathrm{bit}(b, n + m) = \mathrm{bit}(b, n) + \mathrm{bit}(\mathrm{false}, m). $$$$
Lean4
theorem bit_add' : ∀ (b : Bool) (n m : ℕ), bit b (n + m) = bit b n + bit false m
| true, _, _ => by dsimp [bit]; cutsat
| false, _, _ => by dsimp [bit]; cutsat