Theorem: DividedPowerAlgebra.dp_null (DividedPowers/DPAlgebra/Init.lean)

State before:
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
⊢ dp R n 0 = if n = 0 then 1 else 0
Tactic:
cases' Nat.eq_zero_or_pos n with hn hn
State after:
case inl
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
hn : n = 0
⊢ dp R n 0 = if n = 0 then 1 else 0

case inr
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
hn : n > 0
⊢ dp R n 0 = if n = 0 then 1 else 0

State before:
case inl
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
hn : n = 0
⊢ dp R n 0 = if n = 0 then 1 else 0
Tactic:
rw [if_pos hn, hn, dp_zero]
State after:
no goals

State before:
case inr
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
hn : n > 0
⊢ dp R n 0 = if n = 0 then 1 else 0
Tactic:
rw [if_neg (ne_of_gt hn), ← zero_smul R (0 : M), dp_smul]
State after:
case inr
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
hn : n > 0
⊢ 0 ^ n • dp R n 0 = 0

State before:
case inr
R : Type u_1
M : Type u_2
inst✝² : CommSemiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
n : ℕ
hn : n > 0
⊢ 0 ^ n • dp R n 0 = 0
Tactic:
rw [zero_pow (Nat.pos_iff_ne_zero.mp hn), zero_smul]
State after:
no goals