cases b <;> simp [← Nat.two_mul, Nat.mul_add_mod]
case f
b : Bool
n✝ : ℕ
a✝ : bit b n✝ = n✝ → (!decide (bit b n✝ % 2 = 0)) = decide (bit b n✝ % 2 = 1)
⊢ (!decide (bit b n✝ % 2 = 0)) = decide (bit b n✝ % 2 = 1)
no goals