-- Mathlib/RingTheory/DedekindDomain/Factorization.lean
theorem count_mul {I I' : FractionalIdeal R⁰ K} (hI : I ≠ 0) (hI' : I' ≠ 0) :
    count K v (I * I') = count K v I + count K v I'

Proof state:
case intro.intro.intro.intro.intro.intro
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
ha_ne_zero : Associates.mk (Ideal.span {a}) ≠ 0
hJ_ne_zero : Associates.mk J ≠ 0
a' : R
J' : Ideal R
ha' : a' ≠ 0
haJ' : I' = spanSingleton R⁰ ((algebraMap R K) a')⁻¹ * ↑J'
ha'_ne_zero : Associates.mk (Ideal.span {a'}) ≠ 0
⊢ count K v (I * I') = count K v I + count K v I'

Tactic:
have hJ'_ne_zero : Associates.mk J' ≠ 0 :=
  Associates.mk_ne_zero.mpr (ideal_factor_ne_zero hI' haJ')

Result:
case intro.intro.intro.intro.intro.intro
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
ha_ne_zero : Associates.mk (Ideal.span {a}) ≠ 0
hJ_ne_zero : Associates.mk J ≠ 0
a' : R
J' : Ideal R
ha' : a' ≠ 0
haJ' : I' = spanSingleton R⁰ ((algebraMap R K) a')⁻¹ * ↑J'
ha'_ne_zero : Associates.mk (Ideal.span {a'}) ≠ 0
hJ'_ne_zero : Associates.mk J' ≠ 0
⊢ count K v (I * I') = count K v I + count K v I'

Proof state:
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
⊢ count K v (I * I') = count K v I + count K v I'

Tactic:
have hv : Irreducible (Associates.mk v.asIdeal) := by apply v.associates_irreducible

Result:
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
⊢ count K v (I * I') = count K v I + count K v I'

Proof state:
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
ha_ne_zero : Associates.mk (Ideal.span {a}) ≠ 0
hJ_ne_zero : Associates.mk J ≠ 0
a' : R
J' : Ideal R
ha' : a' ≠ 0
haJ' : I' = spanSingleton R⁰ ((algebraMap R K) a')⁻¹ * ↑J'
⊢ ¬a' = 0

Tactic:
exact ha'

Result:
no goals

Proof state:
case intro.intro.intro.intro.intro.intro
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
ha_ne_zero : Associates.mk (Ideal.span {a}) ≠ 0
hJ_ne_zero : Associates.mk J ≠ 0
a' : R
J' : Ideal R
ha' : a' ≠ 0
haJ' : I' = spanSingleton R⁰ ((algebraMap R K) a')⁻¹ * ↑J'
ha'_ne_zero : Associates.mk (Ideal.span {a'}) ≠ 0
hJ'_ne_zero : Associates.mk J' ≠ 0
h_prod : I * I' = spanSingleton R⁰ ((algebraMap R K) (a * a'))⁻¹ * ↑(J * J')
⊢ ↑((Associates.mk v.asIdeal).count (Associates.mk J).factors +
          (Associates.mk v.asIdeal).count (Associates.mk J').factors) -
      ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a})).factors +
          (Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a'})).factors) =
    ↑((Associates.mk v.asIdeal).count (Associates.mk J).factors) -
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a})).factors) +
      (↑((Associates.mk v.asIdeal).count (Associates.mk J').factors) -
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a'})).factors))

Tactic:
push_cast

Result:
case intro.intro.intro.intro.intro.intro
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
ha_ne_zero : Associates.mk (Ideal.span {a}) ≠ 0
hJ_ne_zero : Associates.mk J ≠ 0
a' : R
J' : Ideal R
ha' : a' ≠ 0
haJ' : I' = spanSingleton R⁰ ((algebraMap R K) a')⁻¹ * ↑J'
ha'_ne_zero : Associates.mk (Ideal.span {a'}) ≠ 0
hJ'_ne_zero : Associates.mk J' ≠ 0
h_prod : I * I' = spanSingleton R⁰ ((algebraMap R K) (a * a'))⁻¹ * ↑(J * J')
⊢ ↑((Associates.mk v.asIdeal).count (Associates.mk J).factors) +
        ↑((Associates.mk v.asIdeal).count (Associates.mk J').factors) -
      (↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a})).factors) +
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a'})).factors)) =
    ↑((Associates.mk v.asIdeal).count (Associates.mk J).factors) -
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a})).factors) +
      (↑((Associates.mk v.asIdeal).count (Associates.mk J').factors) -
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a'})).factors))

Proof state:
case intro.intro.intro.intro.intro.intro
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
ha_ne_zero : Associates.mk (Ideal.span {a}) ≠ 0
hJ_ne_zero : Associates.mk J ≠ 0
a' : R
J' : Ideal R
ha' : a' ≠ 0
haJ' : I' = spanSingleton R⁰ ((algebraMap R K) a')⁻¹ * ↑J'
ha'_ne_zero : Associates.mk (Ideal.span {a'}) ≠ 0
hJ'_ne_zero : Associates.mk J' ≠ 0
h_prod : I * I' = spanSingleton R⁰ ((algebraMap R K) (a * a'))⁻¹ * ↑(J * J')
⊢ ↑((Associates.mk v.asIdeal).count (Associates.mk J).factors) +
        ↑((Associates.mk v.asIdeal).count (Associates.mk J').factors) -
      (↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a})).factors) +
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a'})).factors)) =
    ↑((Associates.mk v.asIdeal).count (Associates.mk J).factors) -
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a})).factors) +
      (↑((Associates.mk v.asIdeal).count (Associates.mk J').factors) -
        ↑((Associates.mk v.asIdeal).count (Associates.mk (Ideal.span {a'})).factors))

Tactic:
ring

Result:
no goals

Proof state:
R : Type u_1
inst✝⁴ : CommRing R
K : Type u_2
inst✝³ : Field K
inst✝² : Algebra R K
inst✝¹ : IsFractionRing R K
inst✝ : IsDedekindDomain R
v : HeightOneSpectrum R
I I' : FractionalIdeal R⁰ K
hI : I ≠ 0
hI' : I' ≠ 0
hv : Irreducible (Associates.mk v.asIdeal)
a : R
J : Ideal R
ha : a ≠ 0
haJ : I = spanSingleton R⁰ ((algebraMap R K) a)⁻¹ * ↑J
⊢ ¬a = 0

Tactic:
exact ha

Result:
no goals