English
If m < n, then bit a m < bit b n for any a,b ∈ {true,false}.
Русский
Если m < n, то bit a m < bit b n для любых a,b ∈ {true,false}.
LaTeX
$$$$ \forall (a,b : \mathrm{Bool}) (h : m < n), \; \text{bit}(a,m) < \text{bit}(b,n). $$$$
Lean4
theorem bit_lt_bit (a b) (h : m < n) : bit a m < bit b n :=
calc
bit a m < 2 * n := by cases a <;> dsimp [bit] <;> omega
_ ≤ bit b n := by cases b <;> dsimp [bit] <;> omega