Module: Mathlib.NumberTheory.NumberField.Cyclotomic.Basic

Goal state before:
pp: case e_a.coprime
n₁ n₂ : ℕ
hn₁ : 1 < n₁
hn₂ : 1 < n₂
h : n₁.Coprime n₂
K : Type u
inst✝¹ : Field K
inst✝ : CharZero K
hn : NeZero (n₁ * n₂)
hK : IsCyclotomicExtension {n₁ * n₂} ℚ K
this✝⁴ : NumberField K
this✝³ : NeZero n₁
this✝² : NeZero n₂
ζ : K := zeta (n₁ * n₂) ℚ K
hζ : IsPrimitiveRoot (zeta (n₁ * n₂) ℚ K) (n₁ * n₂)
hζ₁ : IsPrimitiveRoot (zeta (n₁ * n₂) ℚ K ^ n₂) n₁
this✝¹ : IsCyclotomicExtension {n₁} ℚ ↥ℚ⟮zeta (n₁ * n₂) ℚ K ^ n₂⟯
hζ₁' : IsPrimitiveRoot (AdjoinSimple.gen ℚ (ζ ^ n₂)) n₁
hK₁ : (NumberField.discr ↥ℚ⟮ζ ^ n₂⟯).natAbs = n₁ ^ φ n₁ / ∏ p ∈ n₁.primeFactors, p ^ (φ n₁ / (p - 1))
hζ₂ : IsPrimitiveRoot (zeta (n₁ * n₂) ℚ K ^ n₁) n₂
this✝ : IsCyclotomicExtension {n₂} ℚ ↥ℚ⟮zeta (n₁ * n₂) ℚ K ^ n₁⟯
hζ₂' : IsPrimitiveRoot (AdjoinSimple.gen ℚ (ζ ^ n₁)) n₂
hK₂ : (NumberField.discr ↥ℚ⟮ζ ^ n₁⟯).natAbs = n₂ ^ φ n₂ / ∏ p ∈ n₂.primeFactors, p ^ (φ n₂ / (p - 1))
this : IsGalois ℚ ↥ℚ⟮ζ ^ n₂⟯
h_top : ℚ⟮ζ ^ n₂⟯ ⊔ ℚ⟮ζ ^ n₁⟯ = ⊤
h_cpr : IsCoprime (NumberField.discr ↥ℚ⟮ζ ^ n₂⟯) (NumberField.discr ↥ℚ⟮ζ ^ n₁⟯)
h_dsj : ℚ⟮ζ ^ n₂⟯.LinearDisjoint ↥ℚ⟮ζ ^ n₁⟯
h_div₁ : ∏ p ∈ n₁.primeFactors, p ^ (φ n₁ / (p - 1)) ∣ n₁ ^ φ n₁
h_div₂ : ∏ p ∈ n₂.primeFactors, p ^ (φ n₂ / (p - 1)) ∣ n₂ ^ φ n₂
⊢ (NumberField.discr K).natAbs = (n₁ * n₂) ^ φ (n₁ * n₂) / ∏ p ∈ (n₁ * n₂).primeFactors, p ^ (φ (n₁ * n₂) / (p - 1))

Tactic:
rw [natAbs_discr_eq_natAbs_discr_pow_mul_natAbs_discr_pow K ℚ⟮ζ ^ n₂⟯ ℚ⟮ζ ^ n₁⟯ h_dsj h_top
      (isCoprime_differentIdeal_of_isCoprime_discr _ h_cpr), hK₁, hK₂,
      finrank n₁ ℚ⟮ζ ^ n₂⟯, finrank n₂ ℚ⟮ζ ^ n₁⟯, Nat.div_pow h_div₁, Nat.div_pow h_div₂,
      ← Nat.mul_div_mul_comm (pow_dvd_pow_of_dvd h_div₁ n₂.totient)
      (pow_dvd_pow_of_dvd h_div₂ n₁.totient), primeFactors_mul (NeZero.ne _) (NeZero.ne _),
      Finset.prod_union h.disjoint_primeFactors, ← Finset.prod_pow, ← Finset.prod_pow]

Goal state after:
case e_a.coprime
n₁ n₂ : ℕ
hn₁ : 1 < n₁
hn₂ : 1 < n₂
h : n₁.Coprime n₂
K : Type u
inst✝¹ : Field K
inst✝ : CharZero K
hn : NeZero (n₁ * n₂)
hK : IsCyclotomicExtension {n₁ * n₂} ℚ K
this✝⁴ : NumberField K
this✝³ : NeZero n₁
this✝² : NeZero n₂
ζ : K := zeta (n₁ * n₂) ℚ K
hζ : IsPrimitiveRoot (zeta (n₁ * n₂) ℚ K) (n₁ * n₂)
hζ₁ : IsPrimitiveRoot (zeta (n₁ * n₂) ℚ K ^ n₂) n₁
this✝¹ : IsCyclotomicExtension {n₁} ℚ ↥ℚ⟮zeta (n₁ * n₂) ℚ K ^ n₂⟯
hζ₁' : IsPrimitiveRoot (AdjoinSimple.gen ℚ (ζ ^ n₂)) n₁
hK₁ : (NumberField.discr ↥ℚ⟮ζ ^ n₂⟯).natAbs = n₁ ^ φ n₁ / ∏ p ∈ n₁.primeFactors, p ^ (φ n₁ / (p - 1))
hζ₂ : IsPrimitiveRoot (zeta (n₁ * n₂) ℚ K ^ n₁) n₂
this✝ : IsCyclotomicExtension {n₂} ℚ ↥ℚ⟮zeta (n₁ * n₂) ℚ K ^ n₁⟯
hζ₂' : IsPrimitiveRoot (AdjoinSimple.gen ℚ (ζ ^ n₁)) n₂
hK₂ : (NumberField.discr ↥ℚ⟮ζ ^ n₁⟯).natAbs = n₂ ^ φ n₂ / ∏ p ∈ n₂.primeFactors, p ^ (φ n₂ / (p - 1))
this : IsGalois ℚ ↥ℚ⟮ζ ^ n₂⟯
h_top : ℚ⟮ζ ^ n₂⟯ ⊔ ℚ⟮ζ ^ n₁⟯ = ⊤
h_cpr : IsCoprime (NumberField.discr ↥ℚ⟮ζ ^ n₂⟯) (NumberField.discr ↥ℚ⟮ζ ^ n₁⟯)
h_dsj : ℚ⟮ζ ^ n₂⟯.LinearDisjoint ↥ℚ⟮ζ ^ n₁⟯
h_div₁ : ∏ p ∈ n₁.primeFactors, p ^ (φ n₁ / (p - 1)) ∣ n₁ ^ φ n₁
h_div₂ : ∏ p ∈ n₂.primeFactors, p ^ (φ n₂ / (p - 1)) ∣ n₂ ^ φ n₂
⊢ (n₁ ^ φ n₁) ^ φ n₂ * (n₂ ^ φ n₂) ^ φ n₁ /
      ((∏ x ∈ n₁.primeFactors, (x ^ (φ n₁ / (x - 1))) ^ φ n₂) * ∏ x ∈ n₂.primeFactors, (x ^ (φ n₂ / (x - 1))) ^ φ n₁) =
    (n₁ * n₂) ^ φ (n₁ * n₂) /
      ((∏ x ∈ n₁.primeFactors, x ^ (φ (n₁ * n₂) / (x - 1))) * ∏ x ∈ n₂.primeFactors, x ^ (φ (n₁ * n₂) / (x - 1)))