-- Mathlib/Analysis/BoxIntegral/Box/SubboxInduction.lean
theorem subbox_induction_on' {p : Box ι → Prop} (I : Box ι)
    (H_ind : ∀ J ≤ I, (∀ s, p (splitCenterBox J s)) → p J)
    (H_nhds : ∀ z ∈ Box.Icc I, ∃ U ∈ 𝓝[Box.Icc I] z, ∀ J ≤ I, ∀ (m : ℕ), z ∈ Box.Icc J →
      Box.Icc J ⊆ U → (∀ i, J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J) :
    p I

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_ind : ∀ J ≤ I, (∀ (s : Set ι), p (J.splitCenterBox s)) → p J
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
⊢ p I

Tactic:
by_contra hpI

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_ind : ∀ J ≤ I, (∀ (s : Set ι), p (J.splitCenterBox s)) → p J
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
⊢ False

Proof state:
case succ
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
i : ι
m : ℕ
ihm : (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
⊢ (J (m + 1)).upper i - (J (m + 1)).lower i = (I.upper i - I.lower i) / 2 ^ (m + 1)

Tactic:
simp only [pow_succ, J_succ, upper_sub_lower_splitCenterBox, ihm, div_div]

Result:
no goals

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
m : ℕ
i : ι
⊢ (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m

Tactic:
induction' m with m ihm

Result:
case zero
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
i : ι
⊢ (J 0).upper i - (J 0).lower i = (I.upper i - I.lower i) / 2 ^ 0

case succ
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
i : ι
m : ℕ
ihm : (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
⊢ (J (m + 1)).upper i - (J (m + 1)).lower i = (I.upper i - I.lower i) / 2 ^ (m + 1)

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
J : ℕ → Box ι
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
hJsub : ∀ (m : ℕ) (i : ι), (J m).upper i - (J m).lower i = (I.upper i - I.lower i) / 2 ^ m
h0 : J 0 = I
z : ι → ℝ := ⨆ m, (J m).lower
hzJ : ∀ (m : ℕ), z ∈ Box.Icc (J m)
hJl_mem : ∀ (m : ℕ), (J m).lower ∈ Box.Icc I
hJu_mem : ∀ (m : ℕ), (J m).upper ∈ Box.Icc I
hJlz : Tendsto (fun m => (J m).lower) atTop (𝓝 z)
i : ι
⊢ Tendsto (fun i_1 => ((J i_1).upper - (J i_1).lower) i) atTop (𝓝 (0 i))

Tactic:
simpa [hJsub] using
  tendsto_const_nhds.div_atTop (tendsto_pow_atTop_atTop_of_one_lt _root_.one_lt_two)

Result:
no goals

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_ind : ∀ J ≤ I, (∀ (s : Set ι), p (J.splitCenterBox s)) → p J
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
⊢ False

Tactic:
replace H_ind := fun J hJ ↦ not_imp_not.2 (H_ind J hJ)

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
H_ind : ∀ J ≤ I, ¬p J → ¬∀ (s : Set ι), p (J.splitCenterBox s)
⊢ False

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
⊢ False

Tactic:
have hJp : ∀ m, ¬p (J m) :=
  fun m ↦ Nat.recOn m hpI fun m ↦ by simpa only [J_succ] using hs (J m) (hJle m)

Result:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
hJmono : Antitone J
hJle : ∀ (m : ℕ), J m ≤ I
hJp : ∀ (m : ℕ), ¬p (J m)
⊢ False

Proof state:
ι : Type u_1
p : Box ι → Prop
I : Box ι
H_nhds :
  ∀ z ∈ Box.Icc I,
    ∃ U ∈ 𝓝[Box.Icc I] z,
      ∀ J ≤ I,
        ∀ (m : ℕ),
          z ∈ Box.Icc J → Box.Icc J ⊆ U → (∀ (i : ι), J.upper i - J.lower i = (I.upper i - I.lower i) / 2 ^ m) → p J
hpI : ¬p I
s : Box ι → Set ι
hs : ∀ J ≤ I, ¬p J → ¬p (J.splitCenterBox (s J))
J : ℕ → Box ι := fun m => (fun J => J.splitCenterBox (s J))^[m] I
J_succ : ∀ (m : ℕ), J (m + 1) = (J m).splitCenterBox (s (J m))
n : ℕ
⊢ J (n + 1) ≤ J n

Tactic:
simpa [J_succ] using splitCenterBox_le _ _

Result:
no goals