Theorem: Polynomial.int_coeff_of_cyclotomic'
File: Mathlib/RingTheory/Polynomial/Cyclotomic/Basic.lean

Proof steps:
state_before: K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
ζ : K
n : ℕ
h : IsPrimitiveRoot ζ n
⊢ ∃ P, map (Int.castRingHom K) P = cyclotomic' n K ∧ P.degree = (cyclotomic' n K).degree ∧ P.Monic
state_after: K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
ζ : K
n : ℕ
h : IsPrimitiveRoot ζ n
⊢ cyclotomic' n K ∈ lifts (Int.castRingHom K)
tactic: refine lifts_and_degree_eq_and_monic ?_ (cyclotomic'.monic n K)
state_before: K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
ζ : K
n : ℕ
h : IsPrimitiveRoot ζ n
⊢ cyclotomic' n K ∈ lifts (Int.castRingHom K)
state_after: case h
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: induction' n using Nat.strong_induction_on with k ihk generalizing ζ
state_before: case h
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inl
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
ζ : K
ihk : ∀ m < 0, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
h : IsPrimitiveRoot ζ 0
⊢ cyclotomic' 0 K ∈ lifts (Int.castRingHom K)

case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: rcases k.eq_zero_or_pos with (rfl | hpos)
state_before: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: let B : K[X] := ∏ i ∈ Nat.properDivisors k, cyclotomic' i K
state_before: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: have Bmo : B.Monic := by
    apply monic_prod_of_monic
    intro i _
    exact cyclotomic'.monic i K
state_before: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
Bint : B ∈ lifts (Int.castRingHom K)
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: have Bint : B ∈ lifts (Int.castRingHom K) := by
    refine Subsemiring.prod_mem (lifts (Int.castRingHom K)) ?_
    intro x hx
    have xsmall := (Nat.mem_properDivisors.1 hx).2
    obtain ⟨d, hd⟩ := (Nat.mem_properDivisors.1 hx).1
    rw [mul_comm] at hd
    exact ihk x xsmall (h.pow hpos hd)
state_before: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
Bint : B ∈ lifts (Int.castRingHom K)
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
Bint : ∃ q, map (Int.castRingHom K) q = B ∧ q.degree = B.degree ∧ q.Monic
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: replace Bint := lifts_and_degree_eq_and_monic Bint Bmo
state_before: case h.inr
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
Bint : ∃ q, map (Int.castRingHom K) q = B ∧ q.degree = B.degree ∧ q.Monic
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: obtain ⟨B₁, hB₁, _, hB₁mo⟩ := Bint
state_before: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: let Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
state_before: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : 0 + B * cyclotomic' k K = X ^ k - 1 ∧ degree 0 < B.degree
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
tactic: replace huniq := div_modByMonic_unique (cyclotomic' k K) (0 : K[X]) Bmo huniq
state_before: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ cyclotomic' k K ∈ lifts (Int.castRingHom K)
state_after: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ ∃ x, (mapRingHom (Int.castRingHom K)) x = cyclotomic' k K
tactic: simp only [lifts, RingHom.mem_rangeS]
state_before: case h.inr.intro.intro.intro
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ ∃ x, (mapRingHom (Int.castRingHom K)) x = cyclotomic' k K
state_after: case h
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ (mapRingHom (Int.castRingHom K)) Q₁ = cyclotomic' k K
tactic: use Q₁
state_before: case h
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ (mapRingHom (Int.castRingHom K)) Q₁ = cyclotomic' k K
state_after: case h
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ map (Int.castRingHom K) (X ^ k - 1) /ₘ B = (X ^ k - 1) /ₘ B
tactic: rw [coe_mapRingHom, map_divByMonic (Int.castRingHom K) hB₁mo, hB₁, ← huniq.1]
state_before: case h
K✝ : Type u_1
inst✝² : Field K✝
K : Type u_2
inst✝¹ : CommRing K
inst✝ : IsDomain K
k : ℕ
ihk : ∀ m < k, ∀ {ζ : K}, IsPrimitiveRoot ζ m → cyclotomic' m K ∈ lifts (Int.castRingHom K)
ζ : K
h : IsPrimitiveRoot ζ k
hpos : k > 0
B : K[X] := ∏ i ∈ k.properDivisors, cyclotomic' i K
Bmo : B.Monic
B₁ : ℤ[X]
hB₁ : map (Int.castRingHom K) B₁ = B
left✝ : B₁.degree = B.degree
hB₁mo : B₁.Monic
Q₁ : ℤ[X] := (X ^ k - 1) /ₘ B₁
huniq : (X ^ k - 1) /ₘ B = cyclotomic' k K ∧ (X ^ k - 1) %ₘ B = 0
⊢ map (Int.castRingHom K) (X ^ k - 1) /ₘ B = (X ^ k - 1) /ₘ B
state_after: no goals
tactic: simp