-- Mathlib/RingTheory/UniqueFactorizationDomain/FactorSet.lean
theorem dvd_count_of_dvd_count_mul {a b : Associates α} (hb : b ≠ 0)
    {p : Associates α} (hp : Irreducible p) (hab : ∀ d, d ∣ a → d ∣ b → ¬Prime d) {k : ℕ}
    (habk : k ∣ count p (a * b).factors) : k ∣ count p a.factors

Proof state:
case neg.inl
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
hz : p.count a.factors = 0
⊢ k ∣ p.count a.factors

Tactic:
rw [hz]

Result:
case neg.inl
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
hz : p.count a.factors = 0
⊢ k ∣ 0

Proof state:
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
⊢ k ∣ p.count a.factors

Tactic:
by_cases ha : a = 0

Result:
case pos
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : a = 0
⊢ k ∣ p.count a.factors

case neg
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
⊢ k ∣ p.count a.factors

Proof state:
case neg
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
⊢ k ∣ p.count a.factors

Tactic:
rcases count_of_coprime ha hb hab hp with hz | h

Result:
case neg.inl
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
hz : p.count a.factors = 0
⊢ k ∣ p.count a.factors

case neg.inr
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
h : p.count b.factors = 0
⊢ k ∣ p.count a.factors

Proof state:
case neg.inr
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
h : p.count b.factors = 0
⊢ k ∣ p.count a.factors

Tactic:
rw [count_mul ha hb hp, h] at habk

Result:
case neg.inr
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count a.factors + 0
ha : ¬a = 0
h : p.count b.factors = 0
⊢ k ∣ p.count a.factors

Proof state:
case pos
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : a = 0
⊢ k ∣ p.count a.factors

Tactic:
simpa [*] using habk

Result:
no goals

Proof state:
case neg.inl
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count (a * b).factors
ha : ¬a = 0
hz : p.count a.factors = 0
⊢ k ∣ 0

Tactic:
exact dvd_zero k

Result:
no goals

Proof state:
case neg.inr
α : Type u_1
inst✝³ : CancelCommMonoidWithZero α
inst✝² : UniqueFactorizationMonoid α
inst✝¹ : DecidableEq (Associates α)
inst✝ : (p : Associates α) → Decidable (Irreducible p)
a b : Associates α
hb : b ≠ 0
p : Associates α
hp : Irreducible p
hab : ∀ (d : Associates α), d ∣ a → d ∣ b → ¬Prime d
k : ℕ
habk : k ∣ p.count a.factors + 0
ha : ¬a = 0
h : p.count b.factors = 0
⊢ k ∣ p.count a.factors

Tactic:
exact habk

Result:
no goals