Module: Mathlib.MeasureTheory.Covering.Besicovitch

Goal state before:
pp: case ind
α : Type u_1
inst✝¹ : MetricSpace α
β : Type u
inst✝ : Nonempty β
p : TauPackage β α
N : ℕ
hN : IsEmpty (SatelliteConfig α N p.τ)
i : Ordinal.{u}
IH : ∀ y < i, y < p.lastStep → p.color y < N
hi : i < p.lastStep
A : Set ℕ :=
  ⋃ j,
    ⋃ (_ :
      (closedBall (p.c (p.index ↑j)) (p.r (p.index ↑j)) ∩ closedBall (p.c (p.index i)) (p.r (p.index i))).Nonempty),
      {p.color ↑j}
color_i : p.color i = sInf (univ \ A)
N_mem : N ∈ univ \ A
Inf_eq_N : sInf (univ \ A) = N
g : ℕ → Ordinal.{u}
hg :
  ∀ k < N,
    g k < i ∧
      (closedBall (p.c (p.index (g k))) (p.r (p.index (g k))) ∩
            closedBall (p.c (p.index i)) (p.r (p.index i))).Nonempty ∧
        k = p.color (g k)
G : ℕ → Ordinal.{u} := fun n ↦ if n = N then i else g n
color_G : ∀ n ≤ N, p.color (G n) = n
G_lt_last : ∀ n ≤ N, G n < p.lastStep
fGn : ∀ n ≤ N, p.c (p.index (G n)) ∉ p.iUnionUpTo (G n) ∧ p.R (G n) ≤ p.τ * p.r (p.index (G n))
Gab :
  ∀ (a b : Fin N.succ),
    G ↑a < G ↑b →
      p.r (p.index (G ↑a)) ≤ dist (p.c (p.index (G ↑a))) (p.c (p.index (G ↑b))) ∧
        p.r (p.index (G ↑b)) ≤ p.τ * p.r (p.index (G ↑a))
⊢ False

Tactic:
let sc : SatelliteConfig α N p.τ :=
    { c := fun k => p.c (p.index (G k))
      r := fun k => p.r (p.index (G k))
      rpos := fun k => p.rpos (p.index (G k))
      h := by
        intro a b a_ne_b
        wlog G_le : G a ≤ G b generalizing a b
        · exact (this a_ne_b.symm (le_of_not_ge G_le)).symm
        have G_lt : G a < G b := by
          rcases G_le.lt_or_eq with (H | H); · exact H
          have A : (a : ℕ) ≠ b := Fin.val_injective.ne a_ne_b
          rw [← color_G a (Nat.lt_succ_iff.1 a.2), ← color_G b (Nat.lt_succ_iff.1 b.2), H] at A
          exact (A rfl).elim
        exact Or.inl (Gab a b G_lt)
      hlast := by
        intro a ha
        have I : (a : ℕ) < N := ha
        have : G a < G (Fin.last N) := by simp [G, I.ne, (hg a I).1]
        exact Gab _ _ this
      inter := by
        intro a ha
        have I : (a : ℕ) < N := ha
        have J : G (Fin.last N) = i := by dsimp; simp only [G, if_true]
        have K : G a = g a := by simp [G, I.ne]
        convert! dist_le_add_of_nonempty_closedBall_inter_closedBall (hg _ I).2.1 }

Goal state after:
case ind
α : Type u_1
inst✝¹ : MetricSpace α
β : Type u
inst✝ : Nonempty β
p : TauPackage β α
N : ℕ
hN : IsEmpty (SatelliteConfig α N p.τ)
i : Ordinal.{u}
IH : ∀ y < i, y < p.lastStep → p.color y < N
hi : i < p.lastStep
A : Set ℕ :=
  ⋃ j,
    ⋃ (_ :
      (closedBall (p.c (p.index ↑j)) (p.r (p.index ↑j)) ∩ closedBall (p.c (p.index i)) (p.r (p.index i))).Nonempty),
      {p.color ↑j}
color_i : p.color i = sInf (univ \ A)
N_mem : N ∈ univ \ A
Inf_eq_N : sInf (univ \ A) = N
g : ℕ → Ordinal.{u}
hg :
  ∀ k < N,
    g k < i ∧
      (closedBall (p.c (p.index (g k))) (p.r (p.index (g k))) ∩
            closedBall (p.c (p.index i)) (p.r (p.index i))).Nonempty ∧
        k = p.color (g k)
G : ℕ → Ordinal.{u} := fun n ↦ if n = N then i else g n
color_G : ∀ n ≤ N, p.color (G n) = n
G_lt_last : ∀ n ≤ N, G n < p.lastStep
fGn : ∀ n ≤ N, p.c (p.index (G n)) ∉ p.iUnionUpTo (G n) ∧ p.R (G n) ≤ p.τ * p.r (p.index (G n))
Gab :
  ∀ (a b : Fin N.succ),
    G ↑a < G ↑b →
      p.r (p.index (G ↑a)) ≤ dist (p.c (p.index (G ↑a))) (p.c (p.index (G ↑b))) ∧
        p.r (p.index (G ↑b)) ≤ p.τ * p.r (p.index (G ↑a))
sc : SatelliteConfig α N p.τ :=
  { c := fun k ↦ p.c (p.index (G ↑k)), r := fun k ↦ p.r (p.index (G ↑k)), rpos := ⋯, h := ⋯, hlast := ⋯, inter := ⋯ }
⊢ False