Theorem: Filter.tendsto_iff_seq_tendsto
File: Mathlib/Order/Filter/AtTopBot.lean

Proof steps:
state_before: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
⊢ Tendsto f k l ↔ ∀ (x : ℕ → α), Tendsto x atTop k → Tendsto (f ∘ x) atTop l
state_after: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
H : ∀ (x : ℕ → α), Tendsto x atTop k → Tendsto (f ∘ x) atTop l
s : Set β
hs : s ∈ l
⊢ s ∈ map f k
tactic: refine ⟨fun h x hx => h.comp hx, fun H s hs => ?_⟩
state_before: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
H : ∀ (x : ℕ → α), Tendsto x atTop k → Tendsto (f ∘ x) atTop l
s : Set β
hs : s ∈ l
⊢ s ∈ map f k
state_after: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
tactic: contrapose! H
state_before: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
state_after: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
tactic: have : NeBot (k ⊓ 𝓟 (f ⁻¹' sᶜ)) := by simpa [neBot_iff, inf_principal_eq_bot]
state_before: ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
state_after: case intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop (k ⊓ 𝓟 (f ⁻¹' sᶜ))
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
tactic: rcases (k ⊓ 𝓟 (f ⁻¹' sᶜ)).exists_seq_tendsto with ⟨x, hx⟩
state_before: case intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop (k ⊓ 𝓟 (f ⁻¹' sᶜ))
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
state_after: case intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop k ∧ ∀ᶠ (a : ℕ) in atTop, x a ∈ f ⁻¹' sᶜ
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
tactic: rw [tendsto_inf, tendsto_principal] at hx
state_before: case intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop k ∧ ∀ᶠ (a : ℕ) in atTop, x a ∈ f ⁻¹' sᶜ
⊢ ∃ x, Tendsto x atTop k ∧ ¬Tendsto (f ∘ x) atTop l
state_after: case intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop k ∧ ∀ᶠ (a : ℕ) in atTop, x a ∈ f ⁻¹' sᶜ
h : Tendsto (f ∘ x) atTop l
⊢ False
tactic: refine ⟨x, hx.1, fun h => ?_⟩
state_before: case intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop k ∧ ∀ᶠ (a : ℕ) in atTop, x a ∈ f ⁻¹' sᶜ
h : Tendsto (f ∘ x) atTop l
⊢ False
state_after: case intro.intro.intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop k ∧ ∀ᶠ (a : ℕ) in atTop, x a ∈ f ⁻¹' sᶜ
h : Tendsto (f ∘ x) atTop l
N : ℕ
hnmem : x N ∈ f ⁻¹' sᶜ
hmem : (f ∘ x) N ∈ s
⊢ False
tactic: rcases (hx.2.and (h hs)).exists with ⟨N, hnmem, hmem⟩
state_before: case intro.intro.intro
ι : Type u_1
ι' : Type u_2
α : Type u_3
β : Type u_4
γ : Type u_5
f : α → β
k : Filter α
l : Filter β
inst✝ : k.IsCountablyGenerated
s : Set β
hs : s ∈ l
H : s ∉ map f k
this : (k ⊓ 𝓟 (f ⁻¹' sᶜ)).NeBot
x : ℕ → α
hx : Tendsto x atTop k ∧ ∀ᶠ (a : ℕ) in atTop, x a ∈ f ⁻¹' sᶜ
h : Tendsto (f ∘ x) atTop l
N : ℕ
hnmem : x N ∈ f ⁻¹' sᶜ
hmem : (f ∘ x) N ∈ s
⊢ False
state_after: no goals
tactic: exact hnmem hmem