-- Mathlib/Algebra/MvPolynomial/Equiv.lean
theorem image_support_finSuccEquiv {f : MvPolynomial (Fin (n + 1)) R} {i : ℕ} :
    ((finSuccEquiv R n f).coeff i).support.image (Finsupp.cons i) = {m ∈ f.support | m 0 = i}

Proof state:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
h : coeff m f ≠ 0 ∧ m 0 = i
⊢ ¬coeff m f = 0 ∧ m = m

Tactic:
simp [h.1]

Result:
no goals

Proof state:
case h.mp.intro.intro
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
m' : Fin n →₀ ℕ
h : ¬coeff (cons i m') f = 0
hm' : cons i m' = m
⊢ coeff m f ≠ 0 ∧ m 0 = i

Tactic:
simp only [← hm']

Result:
case h.mp.intro.intro
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
m' : Fin n →₀ ℕ
h : ¬coeff (cons i m') f = 0
hm' : cons i m' = m
⊢ coeff (cons i m') f ≠ 0 ∧ (cons i m') 0 = i

Proof state:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
h : coeff m f ≠ 0 ∧ m 0 = i
⊢ ¬coeff (cons i m.tail) f = 0 ∧ cons i m.tail = m

Tactic:
rw [← h.2, cons_tail]

Result:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
h : coeff m f ≠ 0 ∧ m 0 = i
⊢ ¬coeff m f = 0 ∧ m = m

Proof state:
case h.mpr
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ coeff m f ≠ 0 ∧ m 0 = i → ∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m

Tactic:
intro h

Result:
case h.mpr
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
h : coeff m f ≠ 0 ∧ m 0 = i
⊢ ∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m

Proof state:
case h.mp.intro.intro
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
m' : Fin n →₀ ℕ
h : ¬coeff (cons i m') f = 0
hm' : cons i m' = m
⊢ coeff (cons i m') f ≠ 0 ∧ (cons i m') 0 = i

Tactic:
exact ⟨h, by rw [cons_zero]⟩

Result:
no goals

Proof state:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ (∃ a ∈ (((finSuccEquiv R n) f).coeff i).support, cons i a = m) ↔ coeff m f ≠ 0 ∧ m 0 = i

Tactic:
conv_lhs =>
  congr
  ext
  rw [mem_support_iff, finSuccEquiv_coeff_coeff, Ne]

Result:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ (∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m) ↔ coeff m f ≠ 0 ∧ m 0 = i

Proof state:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ m ∈ Finset.image (cons i) (((finSuccEquiv R n) f).coeff i).support ↔ m ∈ Finset.filter (fun m => m 0 = i) f.support

Tactic:
rw [Finset.mem_filter, Finset.mem_image, mem_support_iff]

Result:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ (∃ a ∈ (((finSuccEquiv R n) f).coeff i).support, cons i a = m) ↔ coeff m f ≠ 0 ∧ m 0 = i

Proof state:
case h.mpr
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
h : coeff m f ≠ 0 ∧ m 0 = i
⊢ ∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m

Tactic:
use tail m

Result:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
h : coeff m f ≠ 0 ∧ m 0 = i
⊢ ¬coeff (cons i m.tail) f = 0 ∧ cons i m.tail = m

Proof state:
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
⊢ Finset.image (cons i) (((finSuccEquiv R n) f).coeff i).support = Finset.filter (fun m => m 0 = i) f.support

Tactic:
ext m

Result:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ m ∈ Finset.image (cons i) (((finSuccEquiv R n) f).coeff i).support ↔ m ∈ Finset.filter (fun m => m 0 = i) f.support

Proof state:
case h
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ (∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m) ↔ coeff m f ≠ 0 ∧ m 0 = i

Tactic:
constructor

Result:
case h.mp
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ (∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m) → coeff m f ≠ 0 ∧ m 0 = i

case h.mpr
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ coeff m f ≠ 0 ∧ m 0 = i → ∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m

Proof state:
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
m' : Fin n →₀ ℕ
h : ¬coeff (cons i m') f = 0
hm' : cons i m' = m
⊢ (cons i m') 0 = i

Tactic:
rw [cons_zero]

Result:
no goals

Proof state:
case h.mp
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
⊢ (∃ x, ¬coeff (cons i x) f = 0 ∧ cons i x = m) → coeff m f ≠ 0 ∧ m 0 = i

Tactic:
rintro ⟨m', ⟨h, hm'⟩⟩

Result:
case h.mp.intro.intro
R : Type u
inst✝ : CommSemiring R
n : ℕ
f : MvPolynomial (Fin (n + 1)) R
i : ℕ
m : Fin (n + 1) →₀ ℕ
m' : Fin n →₀ ℕ
h : ¬coeff (cons i m') f = 0
hm' : cons i m' = m
⊢ coeff m f ≠ 0 ∧ m 0 = i