-- Mathlib/MeasureTheory/Integral/IntegralEqImproper.lean
theorem tendsto_zero_of_hasDerivAt_of_integrableOn_Iic
    (hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x)
    (f'int : IntegrableOn f' (Iic a)) (fint : IntegrableOn f (Iic a)) :
    Tendsto f atBot (𝓝 0)

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
A : Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))
this : IntegrableAtFilter (⇑F ∘ f) atBot volume
⊢ limUnder atBot (⇑F ∘ f) = F 0

Tactic:
apply IntegrableAtFilter.eq_zero_of_tendsto this ?_ A

Result:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
A : Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))
this : IntegrableAtFilter (⇑F ∘ f) atBot volume
⊢ ∀ s ∈ atBot, volume s = ⊤

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
⊢ IntegrableOn (⇑F ∘ f') (Iic a) volume

Tactic:
apply F.integrable_comp f'int

Result:
no goals

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
⊢ Tendsto f atBot (𝓝 0)

Tactic:
have A : Tendsto (F ∘ f) atBot (𝓝 (limUnder atBot (F ∘ f))) := by
  apply tendsto_limUnder_of_hasDerivAt_of_integrableOn_Iic Fderiv F'int

Result:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
A : Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))
⊢ Tendsto f atBot (𝓝 0)

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
⊢ Tendsto f atBot (𝓝 0)

Tactic:
have Fint : IntegrableOn (F ∘ f) (Iic a) := by apply F.integrable_comp fint

Result:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
⊢ Tendsto f atBot (𝓝 0)

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
⊢ Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))

Tactic:
apply tendsto_limUnder_of_hasDerivAt_of_integrableOn_Iic Fderiv F'int

Result:
no goals

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
A : Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))
this : IntegrableAtFilter (⇑F ∘ f) atBot volume
⊢ ∀ s ∈ atBot, volume s = ⊤

Tactic:
intro s hs

Result:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
A : Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))
this : IntegrableAtFilter (⇑F ∘ f) atBot volume
s : Set ℝ
hs : s ∈ atBot
⊢ volume s = ⊤

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
⊢ Tendsto f atBot (𝓝 0)

Tactic:
let F : E →L[ℝ] Completion E := Completion.toComplL

Result:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
⊢ Tendsto f atBot (𝓝 0)

Proof state:
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
⊢ IntegrableOn (⇑F ∘ f) (Iic a) volume

Tactic:
apply F.integrable_comp fint

Result:
no goals

Proof state:
case intro
E : Type u_1
f f' : ℝ → E
a : ℝ
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
hderiv : ∀ x ∈ Iic a, HasDerivAt f (f' x) x
f'int : IntegrableOn f' (Iic a) volume
fint : IntegrableOn f (Iic a) volume
F : E →L[ℝ] Completion E := Completion.toComplL
Fderiv : ∀ x ∈ Iic a, HasDerivAt (⇑F ∘ f) (F (f' x)) x
Fint : IntegrableOn (⇑F ∘ f) (Iic a) volume
F'int : IntegrableOn (⇑F ∘ f') (Iic a) volume
A : Tendsto (⇑F ∘ f) atBot (𝓝 (limUnder atBot (⇑F ∘ f)))
this : IntegrableAtFilter (⇑F ∘ f) atBot volume
s : Set ℝ
hs : s ∈ atBot
b : ℝ
hb : ∀ b_1 ≤ b, b_1 ∈ s
⊢ volume (Iic b) ≤ volume s

Tactic:
exact measure_mono hb

Result:
no goals