-- Mathlib/Analysis/Calculus/FDeriv/Extend.lean
theorem hasDerivWithinAt_Iic_of_tendsto_deriv {s : Set ℝ} {e : E} {a : ℝ}
    {f : ℝ → E} (f_diff : DifferentiableOn ℝ f s) (f_lim : ContinuousWithinAt f s a)
    (hs : s ∈ 𝓝[<] a) (f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)) :
    HasDerivWithinAt f e (Iic a) a

Proof state:
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
⊢ ∀ y ∈ Icc b a, ContinuousWithinAt f t y

Tactic:
intro y hy

Result:
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
y : ℝ
hy : y ∈ Icc b a
⊢ ContinuousWithinAt f t y

Proof state:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
⊢ HasDerivWithinAt f e (Iic a) a

Tactic:
have ts : t ⊆ s := Subset.trans Ioo_subset_Ico_self sab

Result:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
⊢ HasDerivWithinAt f e (Iic a) a

Proof state:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
⊢ HasDerivWithinAt f e (Iic a) a

Tactic:
have t_open : IsOpen t := isOpen_Ioo

Result:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
⊢ HasDerivWithinAt f e (Iic a) a

Proof state:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
⊢ HasDerivWithinAt f e (Iic a) a

Tactic:
have t_closure : closure t = Icc b a := closure_Ioo (ne_of_lt ba)

Result:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
⊢ HasDerivWithinAt f e (Iic a) a

Proof state:
case neg
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
y : ℝ
hy : y ∈ Icc b a
h : ¬y = a
this : y ∈ s
⊢ ContinuousWithinAt f t y

Tactic:
exact (f_diff.continuousOn y this).mono ts

Result:
no goals

Proof state:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
t_cont : ∀ y ∈ closure t, ContinuousWithinAt f t y
t_diff' : Tendsto (fun x => fderiv ℝ f x) (𝓝[t] a) (𝓝 (smulRight 1 e))
⊢ HasDerivWithinAt f e (Iic a) a

Tactic:
have : HasDerivWithinAt f e (Icc b a) a := by
  rw [hasDerivWithinAt_iff_hasFDerivWithinAt, ← t_closure]
  exact hasFDerivWithinAt_closure_of_tendsto_fderiv t_diff t_conv t_open t_cont t_diff'

Result:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
t_cont : ∀ y ∈ closure t, ContinuousWithinAt f t y
t_diff' : Tendsto (fun x => fderiv ℝ f x) (𝓝[t] a) (𝓝 (smulRight 1 e))
this : HasDerivWithinAt f e (Icc b a) a
⊢ HasDerivWithinAt f e (Iic a) a

Proof state:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
⊢ HasDerivWithinAt f e (Iic a) a

Tactic:
have t_diff : DifferentiableOn ℝ f t := f_diff.mono ts

Result:
case intro.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
⊢ HasDerivWithinAt f e (Iic a) a

Proof state:
case pos
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℝ E
s : Set ℝ
e : E
a : ℝ
f : ℝ → E
f_diff : DifferentiableOn ℝ f s
f_lim : ContinuousWithinAt f s a
hs : s ∈ 𝓝[<] a
f_lim' : Tendsto (fun x => deriv f x) (𝓝[<] a) (𝓝 e)
b : ℝ
ba : b ∈ Iio a
sab : Ico b a ⊆ s
t : Set ℝ := Ioo b a
ts : t ⊆ s
t_diff : DifferentiableOn ℝ f t
t_conv : Convex ℝ t
t_open : IsOpen t
t_closure : closure t = Icc b a
y : ℝ
hy : y ∈ Icc b a
h : y = a
⊢ ContinuousWithinAt f t a

Tactic:
exact f_lim.mono ts

Result:
no goals