Theorem: UniqueFactorizationMonoid.count_normalizedFactors_eq
File: Mathlib/RingTheory/UniqueFactorizationDomain.lean

Proof steps:
state_before: α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
⊢ count p (normalizedFactors x) = n
state_after: case pos
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : x = 0
⊢ count p (normalizedFactors x) = n

case neg
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ count p (normalizedFactors x) = n
tactic: by_cases hx0 : x = 0
state_before: case neg
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ count p (normalizedFactors x) = n
state_after: case neg
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ ↑(count p (normalizedFactors x)) = ↑n
tactic: rw [← PartENat.natCast_inj]
state_before: case neg
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ ↑(count p (normalizedFactors x)) = ↑n
state_after: case h.e'_2.h.e'_3.h.e'_3
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ p = normalize p

case h.e'_3
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ ↑n = multiplicity p x
tactic: convert (multiplicity_eq_count_normalizedFactors hp hx0).symm
state_before: case h.e'_3
α : Type u_1
R : Type u_2
inst✝⁴ : CancelCommMonoidWithZero R
inst✝³ : UniqueFactorizationMonoid R
inst✝² : NormalizationMonoid R
inst✝¹ : DecidableRel Dvd.dvd
inst✝ : DecidableEq R
p x : R
hp : Irreducible p
hnorm : normalize p = p
n : ℕ
hle : p ^ n ∣ x
hlt : ¬p ^ (n + 1) ∣ x
this : DecidableRel fun x x_1 => x ∣ x_1 := fun x x_1 => Classical.propDecidable ((fun x x_2 => x ∣ x_2) x x_1)
hx0 : ¬x = 0
⊢ ↑n = multiplicity p x
state_after: no goals
tactic: exact (multiplicity.eq_coe_iff.mpr ⟨hle, hlt⟩).symm