Theorem: Polynomial.exists_approx_polynomial_aux
File: Mathlib/NumberTheory/ClassNumber/AdmissibleCardPowDegree.lean

Proof steps:
state_before: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
state_after: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
tactic: have hb : b ≠ 0 := by
    rintro rfl
    specialize hA 0
    rw [degree_zero] at hA
    exact not_lt_of_le bot_le hA
state_before: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
state_after: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
tactic: set f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (natDegree b - j.succ)
state_before: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
state_after: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
tactic: have : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ) := by
    simpa using lt_of_le_of_lt hm (Nat.lt_succ_self m)
state_before: Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
state_after: case intro.intro.intro
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
tactic: obtain ⟨i₀, i₁, i_ne, i_eq⟩ := Fintype.exists_ne_map_eq_of_card_lt f this
state_before: case intro.intro.intro
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
⊢ ∃ i₀ i₁, i₀ ≠ i₁ ∧ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
state_after: case right
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
⊢ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
tactic: use i₀, i₁, i_ne
state_before: case right
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
⊢ (A i₁ - A i₀).degree < ↑(b.natDegree - d)
state_after: case right
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
⊢ (A i₁ - A i₀).coeff j = 0
tactic: refine (degree_lt_iff_coeff_zero _ _).mpr fun j hj => ?_
state_before: case right
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
⊢ (A i₁ - A i₀).coeff j = 0
state_after: case pos
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : b.degree ≤ ↑j
⊢ (A i₁ - A i₀).coeff j = 0

case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : ¬b.degree ≤ ↑j
⊢ (A i₁ - A i₀).coeff j = 0
tactic: by_cases hbj : degree b ≤ j
state_before: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : ¬b.degree ≤ ↑j
⊢ (A i₁ - A i₀).coeff j = 0
state_after: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : ¬b.degree ≤ ↑j
⊢ (A i₁).coeff j = (A i₀).coeff j
tactic: rw [coeff_sub, sub_eq_zero]
state_before: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : ¬b.degree ≤ ↑j
⊢ (A i₁).coeff j = (A i₀).coeff j
state_after: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : ↑j < ↑b.natDegree
⊢ (A i₁).coeff j = (A i₀).coeff j
tactic: rw [not_le, degree_eq_natDegree hb] at hbj
state_before: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj : ↑j < ↑b.natDegree
⊢ (A i₁).coeff j = (A i₀).coeff j
state_after: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj : b.natDegree - d ≤ j
hbj✝ : ↑j < ↑b.natDegree
hbj : j < b.natDegree
⊢ (A i₁).coeff j = (A i₀).coeff j
tactic: have hbj : j < natDegree b := (@WithBot.coe_lt_coe _ _ _).mp hbj
state_before: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj✝ : b.natDegree - d ≤ j
hbj✝ : ↑j < ↑b.natDegree
hbj : j < b.natDegree
hj : b.natDegree - j.succ < d
⊢ (A i₁).coeff j = (A i₀).coeff j
state_after: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this✝ : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj✝ : b.natDegree - d ≤ j
hbj✝ : ↑j < ↑b.natDegree
hbj : j < b.natDegree
hj : b.natDegree - j.succ < d
this : j = b.natDegree - (b.natDegree - j.succ).succ
⊢ (A i₁).coeff j = (A i₀).coeff j
tactic: have : j = b.natDegree - (natDegree b - j.succ).succ := by
    rw [← Nat.succ_sub hbj, Nat.succ_sub_succ, tsub_tsub_cancel_of_le hbj.le]
state_before: case neg
Fq : Type u_1
inst✝¹ : Fintype Fq
inst✝ : Ring Fq
d m : ℕ
hm : Fintype.card Fq ^ d ≤ m
b : Fq[X]
A : Fin m.succ → Fq[X]
hA : ∀ (i : Fin m.succ), (A i).degree < b.degree
hb : b ≠ 0
f : Fin m.succ → Fin d → Fq := fun i j => (A i).coeff (b.natDegree - ↑j.succ)
this✝ : Fintype.card (Fin d → Fq) < Fintype.card (Fin m.succ)
i₀ i₁ : Fin m.succ
i_ne : i₀ ≠ i₁
i_eq : f i₀ = f i₁
j : ℕ
hj✝ : b.natDegree - d ≤ j
hbj✝ : ↑j < ↑b.natDegree
hbj : j < b.natDegree
hj : b.natDegree - j.succ < d
this : j = b.natDegree - (b.natDegree - j.succ).succ
⊢ (A i₁).coeff j = (A i₀).coeff j
state_after: no goals
tactic: convert congr_fun i_eq.symm ⟨natDegree b - j.succ, hj⟩