English
For any α with AddGroupWithOne, (n.bit0 : α) = (n : α) + n.
Русский
Для любого α с AddGroupWithOne: (n.bit0 : α) = (n : α) + n.
LaTeX
$$$$\forall n:\mathrm{ZNum},\ (n.\text{bit0} : \alpha) = (n : \alpha) + n.$$$$
Lean4
@[simp, norm_cast]
theorem cast_bit0 [AddGroupWithOne α] : ∀ n : ZNum, (n.bit0 : α) = (n : α) + n
| 0 => (add_zero _).symm
| pos p => by rw [ZNum.bit0, cast_pos, cast_pos]; rfl
| neg p => by rw [ZNum.bit0, cast_neg, cast_neg, PosNum.cast_bit0, neg_add_rev]