-- Mathlib/RingTheory/Polynomial/Cyclotomic/Eval.lean
theorem eval_one_cyclotomic_not_prime_pow {R : Type*} [Ring R] {n : ℕ}
    (h : ∀ {p : ℕ}, p.Prime → ∀ k : ℕ, p ^ k ≠ n) : eval 1 (cyclotomic n R) = 1

Proof state:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ∏ x ∈ n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n)), eval 1 (cyclotomic x ℤ)
⊢ False

Tactic:
rw [← Finset.prod_sdiff <| show {n} ⊆ _ from _] at this

Result:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ((∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ)) *
        ∏ x ∈ {n}, eval 1 (cyclotomic x ℤ))
⊢ False

R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ∏ x ∈ n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n)), eval 1 (cyclotomic x ℤ)
⊢ {n} ⊆ n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))

Proof state:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : ↑p ∣ eval 1 (cyclotomic n ℤ)
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ((∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ)) *
        ∏ x ∈ {n}, eval 1 (cyclotomic x ℤ))
⊢ False

Tactic:
obtain ⟨t, ht⟩ := hpe

Result:
case intro
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ((∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ)) *
        ∏ x ∈ {n}, eval 1 (cyclotomic x ℤ))
t : ℤ
ht : eval 1 (cyclotomic n ℤ) = ↑p * t
⊢ False

Proof state:
case intro
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
this✝¹ : Fact (Nat.Prime p)
t : ℤ
this✝ :
  ↑n =
    ↑p ^ padicValNat p n * ↑p *
      (t *
        ∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ))
ht : eval 1 (cyclotomic n ℤ) = ↑p * t
this : ↑p ^ padicValNat p n * ↑p ∣ ↑n
⊢ False

Tactic:
simp only [← _root_.pow_succ, ← Int.natAbs_dvd_natAbs, Int.natAbs_ofNat, Int.natAbs_pow] at this

Result:
case intro
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
this✝¹ : Fact (Nat.Prime p)
t : ℤ
this✝ :
  ↑n =
    ↑p ^ padicValNat p n * ↑p *
      (t *
        ∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ))
ht : eval 1 (cyclotomic n ℤ) = ↑p * t
this : p ^ (padicValNat p n + 1) ∣ n
⊢ False

Proof state:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
this : Fact (Nat.Prime p)
⊢ False

Tactic:
have := prod_cyclotomic_eq_geom_sum hn' ℤ

Result:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
this✝ : Fact (Nat.Prime p)
this : ∏ i ∈ n.divisors.erase 1, cyclotomic i ℤ = ∑ i ∈ range n, X ^ i
⊢ False

Proof state:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
⊢ ∀ (p : ℕ), Nat.Prime p → ¬p ∣ (eval 1 (cyclotomic n ℤ)).natAbs

Tactic:
intro p hp hpe

Result:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
⊢ False

Proof state:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : p ∣ (eval 1 (cyclotomic n ℤ)).natAbs
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ((∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ)) *
        ∏ x ∈ {n}, eval 1 (cyclotomic x ℤ))
⊢ False

Tactic:
rw [← Int.natAbs_ofNat p, Int.natAbs_dvd_natAbs] at hpe

Result:
R : Type u_1
inst✝ : Ring R
n : ℕ
h : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
p : ℕ
hp : Nat.Prime p
hpe : ↑p ∣ eval 1 (cyclotomic n ℤ)
this✝ : Fact (Nat.Prime p)
this :
  ↑n =
    ↑p ^ padicValNat p n *
      ((∏ x ∈ (n.divisors.erase 1 \ image (fun t => p ^ (t + 1)) (range (padicValNat p n))) \ {n},
          eval 1 (cyclotomic x ℤ)) *
        ∏ x ∈ {n}, eval 1 (cyclotomic x ℤ))
⊢ False

Proof state:
case inr.inl
R : Type u_1
inst✝ : Ring R
n : ℕ
h✝ : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
h : eval 1 (cyclotomic n ℤ) = 1
⊢ eval 1 (cyclotomic n R) = 1

Tactic:
have := eval_intCast_map (Int.castRingHom R) (cyclotomic n ℤ) 1

Result:
case inr.inl
R : Type u_1
inst✝ : Ring R
n : ℕ
h✝ : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
h : eval 1 (cyclotomic n ℤ) = 1
this : eval (↑1) (map (Int.castRingHom R) (cyclotomic n ℤ)) = (Int.castRingHom R) (eval (↑1) (cyclotomic n ℤ))
⊢ eval 1 (cyclotomic n R) = 1

Proof state:
case inr.inr
R : Type u_1
inst✝ : Ring R
n : ℕ
h✝ : ∀ {p : ℕ}, Nat.Prime p → ∀ (k : ℕ), p ^ k ≠ n
hn' : n > 0
hn : 1 < n
h : eval 1 (cyclotomic n ℤ) = -1
⊢ False

Tactic:
linarith [cyclotomic_nonneg n (le_refl (1 : ℤ))]

Result:
no goals