-- Mathlib/Algebra/Polynomial/BigOperators.lean
theorem leadingCoeff_multiset_prod' (h : (t.map leadingCoeff).prod ≠ 0) :
    t.prod.leadingCoeff = (t.map leadingCoeff).prod

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ a.leadingCoeff * t.prod.leadingCoeff = a.leadingCoeff * (Multiset.map leadingCoeff t).prod

Tactic:
rw [ih]

Result:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ (Multiset.map leadingCoeff t).prod ≠ 0

Proof state:
case empty
R : Type u
inst✝ : CommSemiring R
t : Multiset R[X]
h : (Multiset.map leadingCoeff 0).prod ≠ 0
⊢ (prod 0).leadingCoeff = (Multiset.map leadingCoeff 0).prod

Tactic:
simp

Result:
no goals

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0

Tactic:
exact h

Result:
no goals

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ a.leadingCoeff * t.prod.leadingCoeff ≠ 0

Tactic:
rw [ih]

Result:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0

case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ (Multiset.map leadingCoeff t).prod ≠ 0

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ (Multiset.map leadingCoeff t).prod ≠ 0

Tactic:
simp only [ne_eq]

Result:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ ¬(Multiset.map leadingCoeff t).prod = 0

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ ¬(Multiset.map leadingCoeff t).prod = 0

Tactic:
apply right_ne_zero_of_mul h

Result:
no goals

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ (Multiset.map leadingCoeff t).prod ≠ 0

Tactic:
simp only [ne_eq, not_false_eq_true]

Result:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ ¬(Multiset.map leadingCoeff t).prod = 0

Proof state:
R : Type u
inst✝ : CommSemiring R
t : Multiset R[X]
h : (Multiset.map leadingCoeff t).prod ≠ 0
⊢ t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod

Tactic:
induction' t using Multiset.induction_on with a t ih

Result:
case empty
R : Type u
inst✝ : CommSemiring R
t : Multiset R[X]
h : (Multiset.map leadingCoeff 0).prod ≠ 0
⊢ (prod 0).leadingCoeff = (Multiset.map leadingCoeff 0).prod

case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : (Multiset.map leadingCoeff (a ::ₘ t)).prod ≠ 0
⊢ (a ::ₘ t).prod.leadingCoeff = (Multiset.map leadingCoeff (a ::ₘ t)).prod

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ (a * t.prod).leadingCoeff = a.leadingCoeff * (Multiset.map leadingCoeff t).prod

Tactic:
rw [Polynomial.leadingCoeff_mul']

Result:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ a.leadingCoeff * t.prod.leadingCoeff = a.leadingCoeff * (Multiset.map leadingCoeff t).prod

case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ a.leadingCoeff * t.prod.leadingCoeff ≠ 0

Proof state:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : (Multiset.map leadingCoeff (a ::ₘ t)).prod ≠ 0
⊢ (a ::ₘ t).prod.leadingCoeff = (Multiset.map leadingCoeff (a ::ₘ t)).prod

Tactic:
simp only [Multiset.map_cons, Multiset.prod_cons] at h ⊢

Result:
case cons
R : Type u
inst✝ : CommSemiring R
t✝ : Multiset R[X]
a : R[X]
t : Multiset R[X]
ih : (Multiset.map leadingCoeff t).prod ≠ 0 → t.prod.leadingCoeff = (Multiset.map leadingCoeff t).prod
h : a.leadingCoeff * (Multiset.map leadingCoeff t).prod ≠ 0
⊢ (a * t.prod).leadingCoeff = a.leadingCoeff * (Multiset.map leadingCoeff t).prod