l3lab/ntp-mathlib huggingface dataset:
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · 

Proof state:
case hB'
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
x : ℝ
hx : x ∈ Icc a b
r : ℝ
hr : r > 0
⊢ ∀ x ∈ Ico a b, HasDerivWithinAt (fun x => B x + r * (x - a)) (?m.13033 x) (Ici x) x

Next tactic:
intro x hx
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      

Proof state:
case hB'
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
x✝ : ℝ
hx✝ : x✝ ∈ Icc a b
r : ℝ
hr : r > 0
x : ℝ
hx : x ∈ Ico a b
⊢ HasDerivWithinAt (fun x => B x + r * (x - a)) (?m.13033 x) (Ici x) x

Next tactic:
exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · 

Proof state:
case bound
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
x : ℝ
hx : x ∈ Icc a b
r : ℝ
hr : r > 0
⊢ ∀ x ∈ Ico a b, f x = B x + r * (x - a) → B' x < B' x + r * 1

Next tactic:
intro x _ _
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      

Proof state:
case bound
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
x✝ : ℝ
hx : x✝ ∈ Icc a b
r : ℝ
hr : r > 0
x : ℝ
a✝¹ : x ∈ Ico a b
a✝ : f x = B x + r * (x - a)
⊢ B' x < B' x + r * 1

Next tactic:
rw [mul_one]
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      

Proof state:
case bound
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
x✝ : ℝ
hx : x✝ ∈ Icc a b
r : ℝ
hr : r > 0
x : ℝ
a✝¹ : x ∈ Ico a b
a✝ : f x = B x + r * (x - a)
⊢ B' x < B' x + r

Next tactic:
exact (lt_add_iff_pos_right _).2 hr
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      exact (lt_add_iff_pos_right _).2 hr
    

Proof state:
case a
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
x : ℝ
hx : x ∈ Icc a b
r : ℝ
hr : r > 0
⊢ x ∈ Icc a b

Next tactic:
exact hx
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      exact (lt_add_iff_pos_right _).2 hr
    exact hx
  

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a)
⊢ ∀ ⦃x : ℝ⦄, x ∈ Icc a b → f x ≤ B x

Next tactic:
intro x hx
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      exact (lt_add_iff_pos_right _).2 hr
    exact hx
  intro x hx
  

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a)
x : ℝ
hx : x ∈ Icc a b
⊢ f x ≤ B x

Next tactic:
have : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0 :=
    continuousWithinAt_const.add (continuousWithinAt_id.mul continuousWithinAt_const)
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      exact (lt_add_iff_pos_right _).2 hr
    exact hx
  intro x hx
  have : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0 :=
    continuousWithinAt_const.add (continuousWithinAt_id.mul continuousWithinAt_const)
  

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a)
x : ℝ
hx : x ∈ Icc a b
this : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0
⊢ f x ≤ B x

Next tactic:
convert continuousWithinAt_const.closure_le _ this (Hr x hx) using 1
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      exact (lt_add_iff_pos_right _).2 hr
    exact hx
  intro x hx
  have : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0 :=
    continuousWithinAt_const.add (continuousWithinAt_id.mul continuousWithinAt_const)
  convert continuousWithinAt_const.closure_le _ this (Hr x hx) using 1 <;> 

Proof state:
case h.e'_4
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a)
x : ℝ
hx : x ∈ Icc a b
this : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0
⊢ B x = B x + 0 * (x - a)

Next tactic:
simp
/-- General fencing theorem for continuous functions with an estimate on the derivative.
Let `f` and `B` be continuous functions on `[a, b]` such that

* `f a ≤ B a`;
* `B` has right derivative `B'` at every point of `[a, b)`;
* for each `x ∈ [a, b)` the right-side limit inferior of `(f z - f x) / (z - x)`
  is bounded above by `B'`.

Then `f x ≤ B x` everywhere on `[a, b]`. -/
theorem image_le_of_liminf_slope_right_le_deriv_boundary {f : ℝ → ℝ} {a b : ℝ}
    (hf : ContinuousOn f (Icc a b)) {B B' : ℝ → ℝ} (ha : f a ≤ B a) (hB : ContinuousOn B (Icc a b))
    (hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x)
    -- `bound` actually says `liminf (f z - f x) / (z - x) ≤ B' x`
    (bound : ∀ x ∈ Ico a b, ∀ r, B' x < r → ∃ᶠ z in 𝓝[>] x, slope f x z < r) :
    ∀ ⦃x⦄, x ∈ Icc a b → f x ≤ B x := by
  have Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a) := fun x hx r hr => by
    apply image_le_of_liminf_slope_right_lt_deriv_boundary' hf bound
    · rwa [sub_self, mul_zero, add_zero]
    · exact hB.add (continuousOn_const.mul (continuousOn_id.sub continuousOn_const))
    · intro x hx
      exact (hB' x hx).add (((hasDerivWithinAt_id x (Ici x)).sub_const a).const_mul r)
    · intro x _ _
      rw [mul_one]
      exact (lt_add_iff_pos_right _).2 hr
    exact hx
  intro x hx
  have : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0 :=
    continuousWithinAt_const.add (continuousWithinAt_id.mul continuousWithinAt_const)
  convert continuousWithinAt_const.closure_le _ this (Hr x hx) using 1 <;> 

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → ℝ
a b : ℝ
hf : ContinuousOn f (Icc a b)
B B' : ℝ → ℝ
ha : f a ≤ B a
hB : ContinuousOn B (Icc a b)
hB' : ∀ x ∈ Ico a b, HasDerivWithinAt B (B' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ∀ (r : ℝ), B' x < r → ∃ᶠ (z : ℝ) in 𝓝[>] x, slope f x z < r
Hr : ∀ x ∈ Icc a b, ∀ r > 0, f x ≤ B x + r * (x - a)
x : ℝ
hx : x ∈ Icc a b
this : ContinuousWithinAt (fun r => B x + r * (x - a)) (Ioi 0) 0
⊢ 0 ∈ closure (Ioi 0)

Next tactic:
simp
/-- A function on `[a, b]` with the norm of the right derivative bounded by `C`
satisfies `‖f x - f a‖ ≤ C * (x - a)`. -/
theorem norm_image_sub_le_of_norm_deriv_right_le_segment {f' : ℝ → E} {C : ℝ}
    (hf : ContinuousOn f (Icc a b)) (hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x)
    (bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C) : ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a) := by
  

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → E
a b : ℝ
f' : ℝ → E
C : ℝ
hf : ContinuousOn f (Icc a b)
hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C
⊢ ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a)

Next tactic:
let g x := f x - f a
/-- A function on `[a, b]` with the norm of the right derivative bounded by `C`
satisfies `‖f x - f a‖ ≤ C * (x - a)`. -/
theorem norm_image_sub_le_of_norm_deriv_right_le_segment {f' : ℝ → E} {C : ℝ}
    (hf : ContinuousOn f (Icc a b)) (hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x)
    (bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C) : ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a) := by
  let g x := f x - f a
  

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → E
a b : ℝ
f' : ℝ → E
C : ℝ
hf : ContinuousOn f (Icc a b)
hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C
g : ℝ → E := fun x => f x - f a
⊢ ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a)

Next tactic:
have hg : ContinuousOn g (Icc a b) := hf.sub continuousOn_const
/-- A function on `[a, b]` with the norm of the right derivative bounded by `C`
satisfies `‖f x - f a‖ ≤ C * (x - a)`. -/
theorem norm_image_sub_le_of_norm_deriv_right_le_segment {f' : ℝ → E} {C : ℝ}
    (hf : ContinuousOn f (Icc a b)) (hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x)
    (bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C) : ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a) := by
  let g x := f x - f a
  have hg : ContinuousOn g (Icc a b) := hf.sub continuousOn_const
  

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → E
a b : ℝ
f' : ℝ → E
C : ℝ
hf : ContinuousOn f (Icc a b)
hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C
g : ℝ → E := fun x => f x - f a
hg : ContinuousOn g (Icc a b)
⊢ ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a)

Next tactic:
have hg' : ∀ x ∈ Ico a b, HasDerivWithinAt g (f' x) (Ici x) x := by
    intro x hx
    simpa using (hf' x hx).sub (hasDerivWithinAt_const _ _ _)
/-- A function on `[a, b]` with the norm of the right derivative bounded by `C`
satisfies `‖f x - f a‖ ≤ C * (x - a)`. -/
theorem norm_image_sub_le_of_norm_deriv_right_le_segment {f' : ℝ → E} {C : ℝ}
    (hf : ContinuousOn f (Icc a b)) (hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x)
    (bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C) : ∀ x ∈ Icc a b, ‖f x - f a‖ ≤ C * (x - a) := by
  let g x := f x - f a
  have hg : ContinuousOn g (Icc a b) := hf.sub continuousOn_const
  have hg' : ∀ x ∈ Ico a b, HasDerivWithinAt g (f' x) (Ici x) x := by
    

Proof state:
E : Type u_1
inst✝³ : NormedAddCommGroup E
inst✝² : NormedSpace ℝ E
F : Type u_2
inst✝¹ : NormedAddCommGroup F
inst✝ : NormedSpace ℝ F
f : ℝ → E
a b : ℝ
f' : ℝ → E
C : ℝ
hf : ContinuousOn f (Icc a b)
hf' : ∀ x ∈ Ico a b, HasDerivWithinAt f (f' x) (Ici x) x
bound : ∀ x ∈ Ico a b, ‖f' x‖ ≤ C
g : ℝ → E := fun x => f x - f a
hg : ContinuousOn g (Icc a b)
⊢ ∀ x ∈ Ico a b, HasDerivWithinAt g (f' x) (Ici x) x

Next tactic:
intro x hx