Theorem: hofer
File: Mathlib/Analysis/Hofer.lean

tactic: by_contra H
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
⊢ ∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'

tactic: have reformulation : ∀ (x') (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x' := by
  intro x' k
  rw [div_mul_eq_mul_div, le_div_iff, mul_assoc, mul_le_mul_left ε_pos, mul_comm]
  positivity
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
⊢ False

tactic: replace H :
  ∀ k : ℕ, ∀ x', d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
⊢ False

tactic: clear reformulation
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
H : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y
⊢ False

tactic: haveI : Nonempty X := ⟨x⟩
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y
⊢ False

tactic: choose! F hF using H
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y
this : Nonempty X
⊢ False

tactic: let u : ℕ → X := fun n => Nat.recOn n x F
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
hF : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → d x' (F k x') ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ (F k x')
⊢ False

tactic: have hu :
  ∀ n,
    d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) →
      d (u n) (u <| n + 1) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u <| n + 1) := by
  intro n
  exact hF n (u n)
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
hF : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → d x' (F k x') ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ (F k x')
u : ℕ → X := fun n => Nat.recOn n x F
⊢ False

tactic: clear hF
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
hF : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → d x' (F k x') ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ (F k x')
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
⊢ False

tactic: cases' forall_and.mp key with key₁ key₂
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
key : ∀ (n : ℕ), d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
⊢ False

tactic: clear hu key
state_before: case intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
key : ∀ (n : ℕ), d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
⊢ False

tactic: have cauchy_u : CauchySeq u := by
  refine' cauchySeq_of_le_geometric _ ε one_half_lt_one fun n => _
  simpa only [one_div, inv_pow] using key₁ n
state_before: case intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
⊢ False

tactic: obtain ⟨y, limy⟩ : ∃ y, Tendsto u atTop (𝓝 y)
state_before: case intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
⊢ False

tactic: exact CompleteSpace.complete cauchy_u
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
⊢ ∃ y, Tendsto u atTop (𝓝 y)

case intro.intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
⊢ False

tactic: have lim_top : Tendsto (ϕ ∘ u) atTop atTop := by
  let v n := (ϕ ∘ u) (n + 1)
  suffices Tendsto v atTop atTop by rwa [tendsto_add_atTop_iff_nat] at this
  have hv₀ : 0 < v 0 := by
    have : 0 ≤ ϕ (u 0) := nonneg x
    calc
      0 ≤ 2 * ϕ (u 0) := (zero_le_mul_left zero_lt_two).mpr this
      _ < ϕ (u (0 + 1)) := key₂ 0
  apply tendsto_atTop_of_geom_le hv₀ one_lt_two
  exact fun n => (key₂ (n + 1)).le
state_before: case intro.intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
⊢ False

tactic: have lim : Tendsto (ϕ ∘ u) atTop (𝓝 (ϕ y)) := Tendsto.comp cont.continuousAt limy
state_before: case intro.intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
lim_top : Tendsto (ϕ ∘ u) atTop atTop
⊢ False

tactic: exact not_tendsto_atTop_of_tendsto_nhds lim lim_top
state_before: case intro.intro
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
lim_top : Tendsto (ϕ ∘ u) atTop atTop
lim : Tendsto (ϕ ∘ u) atTop (𝓝 (ϕ y))
⊢ False

tactic: intro x' k
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
⊢ ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'

tactic: rw [div_mul_eq_mul_div, le_div_iff, mul_assoc, mul_le_mul_left ε_pos, mul_comm]
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
x' : X
k : ℕ
⊢ ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'

tactic: positivity
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
x' : X
k : ℕ
⊢ 0 < 2 ^ k

tactic: intro k x'
state_before: case H
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
⊢ ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y

tactic: push_neg at H
state_before: case H
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
H : ¬∃ ε', ε' > 0 ∧ ∃ x', ε' ≤ ε ∧ d x' x ≤ 2 * ε ∧ ε * ϕ x ≤ ε' * ϕ x' ∧ ∀ (y : X), d x' y ≤ ε' → ϕ y ≤ 2 * ϕ x'
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
k : ℕ
x' : X
⊢ d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y

tactic: have := H (ε / 2 ^ k) (by simp [ε_pos]) x' (by simp [ε_pos.le, one_le_two])
state_before: case H
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
k : ℕ
x' : X
H : ∀ (ε' : ℝ), ε' > 0 → ∀ (x' : X), ε' ≤ ε → d x' x ≤ 2 * ε → ε * ϕ x ≤ ε' * ϕ x' → ∃ y, d x' y ≤ ε' ∧ 2 * ϕ x' < ϕ y
⊢ d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y

tactic: simpa [reformulation] using this
state_before: case H
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
k : ℕ
x' : X
H : ∀ (ε' : ℝ), ε' > 0 → ∀ (x' : X), ε' ≤ ε → d x' x ≤ 2 * ε → ε * ϕ x ≤ ε' * ϕ x' → ∃ y, d x' y ≤ ε' ∧ 2 * ϕ x' < ϕ y
this : d x' x ≤ 2 * ε → ε * ϕ x ≤ ε / 2 ^ k * ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y
⊢ d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → ∃ y, d x' y ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ y

tactic: simp [ε_pos]
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
k : ℕ
x' : X
H : ∀ (ε' : ℝ), ε' > 0 → ∀ (x' : X), ε' ≤ ε → d x' x ≤ 2 * ε → ε * ϕ x ≤ ε' * ϕ x' → ∃ y, d x' y ≤ ε' ∧ 2 * ϕ x' < ϕ y
⊢ ε / 2 ^ k > 0

tactic: simp [ε_pos.le, one_le_two]
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
reformulation : ∀ (x' : X) (k : ℕ), ε * ϕ x ≤ ε / 2 ^ k * ϕ x' ↔ 2 ^ k * ϕ x ≤ ϕ x'
k : ℕ
x' : X
H : ∀ (ε' : ℝ), ε' > 0 → ∀ (x' : X), ε' ≤ ε → d x' x ≤ 2 * ε → ε * ϕ x ≤ ε' * ϕ x' → ∃ y, d x' y ≤ ε' ∧ 2 * ϕ x' < ϕ y
⊢ ε / 2 ^ k ≤ ε

tactic: intro n
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
hF : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → d x' (F k x') ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ (F k x')
u : ℕ → X := fun n => Nat.recOn n x F
⊢ ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))

tactic: exact hF n (u n)
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
hF : ∀ (k : ℕ) (x' : X), d x' x ≤ 2 * ε ∧ 2 ^ k * ϕ x ≤ ϕ x' → d x' (F k x') ≤ ε / 2 ^ k ∧ 2 * ϕ x' < ϕ (F k x')
u : ℕ → X := fun n => Nat.recOn n x F
n : ℕ
⊢ d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))

tactic: intro n
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
⊢ ∀ (n : ℕ), d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))

tactic: induction' n using Nat.case_strong_induction_on with n IH
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
⊢ d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))

tactic: have A : d (u (n + 1)) x ≤ 2 * ε := by
  rw [dist_comm]
  let r := range (n + 1) calc
    d (u 0) (u (n + 1)) ≤ ∑ i in r, d (u i) (u <| i + 1) := dist_le_range_sum_dist u (n + 1)
    _ ≤ ∑ i in r, ε / 2 ^ i :=
      (sum_le_sum fun i i_in => (IH i <| Nat.lt_succ_iff.mp <| Finset.mem_range.mp i_in).1)
    _ = ∑ i in r, (1 / 2) ^ i * ε := by
      congr with i
      field_simp
    _ = (∑ i in r, ((1 : ℝ) / 2) ^ i) * ε := Finset.sum_mul.symm
    _ ≤ 2 * ε := by gcongr; apply sum_geometric_two_le
state_before: case hi
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
⊢ d (u (Nat.succ n)) (u (Nat.succ n + 1)) ≤ ε / 2 ^ Nat.succ n ∧ 2 * ϕ (u (Nat.succ n)) < ϕ (u (Nat.succ n + 1))

tactic: have B : 2 ^ (n + 1) * ϕ x ≤ ϕ (u (n + 1)) := by
  refine' @geom_le (ϕ ∘ u) _ zero_le_two (n + 1) fun m hm => _
  exact (IH _ <| Nat.lt_add_one_iff.1 hm).2.le
state_before: case hi
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
A : d (u (n + 1)) x ≤ 2 * ε
⊢ d (u (Nat.succ n)) (u (Nat.succ n + 1)) ≤ ε / 2 ^ Nat.succ n ∧ 2 * ϕ (u (Nat.succ n)) < ϕ (u (Nat.succ n + 1))

tactic: exact hu (n + 1) ⟨A, B⟩
state_before: case hi
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
A : d (u (n + 1)) x ≤ 2 * ε
B : 2 ^ (n + 1) * ϕ x ≤ ϕ (u (n + 1))
⊢ d (u (Nat.succ n)) (u (Nat.succ n + 1)) ≤ ε / 2 ^ Nat.succ n ∧ 2 * ϕ (u (Nat.succ n)) < ϕ (u (Nat.succ n + 1))

tactic: specialize hu 0
state_before: case hz
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
⊢ d (u 0) (u (0 + 1)) ≤ ε / 2 ^ 0 ∧ 2 * ϕ (u 0) < ϕ (u (0 + 1))

tactic: simpa [mul_nonneg_iff, zero_le_one, ε_pos.le, le_refl] using hu
state_before: case hz
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu : d (u 0) x ≤ 2 * ε ∧ 2 ^ 0 * ϕ x ≤ ϕ (u 0) → d (u 0) (u (0 + 1)) ≤ ε / 2 ^ 0 ∧ 2 * ϕ (u 0) < ϕ (u (0 + 1))
⊢ d (u 0) (u (0 + 1)) ≤ ε / 2 ^ 0 ∧ 2 * ϕ (u 0) < ϕ (u (0 + 1))

tactic: rw [dist_comm]
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
⊢ d (u (n + 1)) x ≤ 2 * ε

tactic: let r := range (n + 1)
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
⊢ d x (u (n + 1)) ≤ 2 * ε

tactic: calc
  d (u 0) (u (n + 1)) ≤ ∑ i in r, d (u i) (u <| i + 1) := dist_le_range_sum_dist u (n + 1)
  _ ≤ ∑ i in r, ε / 2 ^ i :=
    (sum_le_sum fun i i_in => (IH i <| Nat.lt_succ_iff.mp <| Finset.mem_range.mp i_in).1)
  _ = ∑ i in r, (1 / 2) ^ i * ε := by
    congr with i
    field_simp
  _ = (∑ i in r, ((1 : ℝ) / 2) ^ i) * ε := Finset.sum_mul.symm
  _ ≤ 2 * ε := by gcongr; apply sum_geometric_two_le
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
r : Finset ℕ := range (n + 1)
⊢ d x (u (n + 1)) ≤ 2 * ε

tactic: congr with i
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
r : Finset ℕ := range (n + 1)
⊢ ∑ i in r, ε / 2 ^ i = ∑ i in r, (1 / 2) ^ i * ε

tactic: field_simp
state_before: case e_f.h
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
r : Finset ℕ := range (n + 1)
i : ℕ
⊢ ε / 2 ^ i = (1 / 2) ^ i * ε

tactic: gcongr
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
r : Finset ℕ := range (n + 1)
⊢ (∑ i in r, (1 / 2) ^ i) * ε ≤ 2 * ε

tactic: apply sum_geometric_two_le
state_before: case h
X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
r : Finset ℕ := range (n + 1)
⊢ ∑ i in r, (1 / 2) ^ i ≤ 2

tactic: refine' @geom_le (ϕ ∘ u) _ zero_le_two (n + 1) fun m hm => _
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
A : d (u (n + 1)) x ≤ 2 * ε
⊢ 2 ^ (n + 1) * ϕ x ≤ ϕ (u (n + 1))

tactic: exact (IH _ <| Nat.lt_add_one_iff.1 hm).2.le
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
hu :
  ∀ (n : ℕ), d (u n) x ≤ 2 * ε ∧ 2 ^ n * ϕ x ≤ ϕ (u n) → d (u n) (u (n + 1)) ≤ ε / 2 ^ n ∧ 2 * ϕ (u n) < ϕ (u (n + 1))
n : ℕ
IH : ∀ (m : ℕ), m ≤ n → d (u m) (u (m + 1)) ≤ ε / 2 ^ m ∧ 2 * ϕ (u m) < ϕ (u (m + 1))
A : d (u (n + 1)) x ≤ 2 * ε
m : ℕ
hm : m < n + 1
⊢ 2 * (ϕ ∘ u) m ≤ (ϕ ∘ u) (m + 1)

tactic: refine' cauchySeq_of_le_geometric _ ε one_half_lt_one fun n => _
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
⊢ CauchySeq u

tactic: simpa only [one_div, inv_pow] using key₁ n
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
n : ℕ
⊢ d (u n) (u (n + 1)) ≤ ε * (1 / 2) ^ n

tactic: let v n := (ϕ ∘ u) (n + 1)
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
⊢ Tendsto (ϕ ∘ u) atTop atTop

tactic: suffices Tendsto v atTop atTop by rwa [tendsto_add_atTop_iff_nat] at this
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
⊢ Tendsto (ϕ ∘ u) atTop atTop

tactic: have hv₀ : 0 < v 0 := by
  have : 0 ≤ ϕ (u 0) := nonneg x
  calc
    0 ≤ 2 * ϕ (u 0) := (zero_le_mul_left zero_lt_two).mpr this
    _ < ϕ (u (0 + 1)) := key₂ 0
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
⊢ Tendsto v atTop atTop

tactic: apply tendsto_atTop_of_geom_le hv₀ one_lt_two
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
hv₀ : 0 < v 0
⊢ Tendsto v atTop atTop

tactic: exact fun n => (key₂ (n + 1)).le
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
hv₀ : 0 < v 0
⊢ ∀ (n : ℕ), 2 * v n ≤ v (n + 1)

tactic: rwa [tendsto_add_atTop_iff_nat] at this
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this✝ : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
this : Tendsto v atTop atTop
⊢ Tendsto (ϕ ∘ u) atTop atTop

tactic: have : 0 ≤ ϕ (u 0) := nonneg x
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
⊢ 0 < v 0

tactic: calc
  0 ≤ 2 * ϕ (u 0) := (zero_le_mul_left zero_lt_two).mpr this
  _ < ϕ (u (0 + 1)) := key₂ 0
state_before: X : Type u_1
inst✝¹ : MetricSpace X
inst✝ : CompleteSpace X
x : X
ε : ℝ
ε_pos : 0 < ε
ϕ : X → ℝ
cont : Continuous ϕ
nonneg : ∀ (y : X), 0 ≤ ϕ y
this✝ : Nonempty X
F : ℕ → X → X
u : ℕ → X := fun n => Nat.recOn n x F
key₁ : ∀ (x : ℕ), d (u x) (u (x + 1)) ≤ ε / 2 ^ x
key₂ : ∀ (x : ℕ), 2 * ϕ (u x) < ϕ (u (x + 1))
cauchy_u : CauchySeq u
y : X
limy : Tendsto u atTop (𝓝 y)
v : ℕ → ℝ := fun n => (ϕ ∘ u) (n + 1)
this : 0 ≤ ϕ (u 0)
⊢ 0 < v 0