Theorem: Asymptotics.superpolynomialDecay_iff_zpow_tendsto_zero
File: Mathlib/Analysis/Asymptotics/SuperpolynomialDecay.lean

tactic: refine' ⟨fun h z => _, fun h n => by simpa only [zpow_ofNat] using h (n : ℤ)⟩
state_before: α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
⊢ SuperpolynomialDecay l k f ↔ ∀ (z : ℤ), Tendsto (fun a => k a ^ z * f a) l (𝓝 0)

tactic: by_cases hz : 0 ≤ z
state_before: α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℤ
⊢ Tendsto (fun a => k a ^ z * f a) l (𝓝 0)

tactic: simpa only [zpow_ofNat] using h (n : ℤ)
state_before: α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : ∀ (z : ℤ), Tendsto (fun a => k a ^ z * f a) l (𝓝 0)
n : ℕ
⊢ Tendsto (fun a => k a ^ n * f a) l (𝓝 0)

tactic: unfold Tendsto
state_before: case pos
α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℤ
hz : 0 ≤ z
⊢ Tendsto (fun a => k a ^ z * f a) l (𝓝 0)

tactic: lift z to ℕ using hz
state_before: case pos
α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℤ
hz : 0 ≤ z
⊢ Filter.map (fun a => k a ^ z * f a) l ≤ 𝓝 0

tactic: simpa using h z
state_before: case pos.intro
α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℕ
⊢ Filter.map (fun a => k a ^ ↑z * f a) l ≤ 𝓝 0

tactic: have : Tendsto (fun a => k a ^ z) l (𝓝 0) :=
  Tendsto.comp (tendsto_zpow_atTop_zero (not_le.1 hz)) hk
state_before: case neg
α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℤ
hz : ¬0 ≤ z
⊢ Tendsto (fun a => k a ^ z * f a) l (𝓝 0)

tactic: have h : Tendsto f l (𝓝 0) := by simpa using h 0
state_before: case neg
α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℤ
hz : ¬0 ≤ z
this : Tendsto (fun a => k a ^ z) l (𝓝 0)
⊢ Tendsto (fun a => k a ^ z * f a) l (𝓝 0)

tactic: exact MulZeroClass.zero_mul (0 : β) ▸ this.mul h
state_before: case neg
α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h✝ : SuperpolynomialDecay l k f
z : ℤ
hz : ¬0 ≤ z
this : Tendsto (fun a => k a ^ z) l (𝓝 0)
h : Tendsto f l (𝓝 0)
⊢ Tendsto (fun a => k a ^ z * f a) l (𝓝 0)

tactic: simpa using h 0
state_before: α : Type u_1
β : Type u_2
l : Filter α
k f g g' : α → β
inst✝² : TopologicalSpace β
inst✝¹ : LinearOrderedField β
inst✝ : OrderTopology β
hk : Tendsto k l atTop
h : SuperpolynomialDecay l k f
z : ℤ
hz : ¬0 ≤ z
this : Tendsto (fun a => k a ^ z) l (𝓝 0)
⊢ Tendsto f l (𝓝 0)