mathlib-initiative/mathlib-tactics huggingface dataset:
Module: Mathlib.Algebra.Polynomial.Eval.Degree

Goal state before:
pp: R : Type u
S : Type v
inst✝¹ : Semiring R
inst✝ : Semiring S
f : R →+* S
p : R[X]
hp : p.Monic
hfp : map f p = 0
x : R
⊢ f x = f x * f p.leadingCoeff

Tactic:
by simp only [mul_one, hp.leadingCoeff, f.map_one]

Goal state after:
Module: Mathlib.Algebra.Polynomial.Eval.Degree

Goal state before:
pp: R : Type u
S : Type v
inst✝¹ : Semiring R
inst✝ : Semiring S
p : R[X]
f : R →+* S
hf : f p.leadingCoeff ≠ 0
⊢ (map f p).leadingCoeff = f p.leadingCoeff

Tactic:
unfold leadingCoeff
  rw [coeff_map, natDegree_map_of_leadingCoeff_ne_zero f hf]

Goal state after:
Module: Mathlib.Algebra.Polynomial.AlgebraMap

Goal state before:
pp: R : Type u
S : Type v
T : Type w
A : Type z
A' : Type u_1
B : Type u_2
a b : R
n : ℕ
inst✝⁴ : CommSemiring R
inst✝³ : Semiring A
inst✝² : Semiring B
inst✝¹ : Algebra R A
inst✝ : Algebra R B
p✝ q r✝ : R[X]
r : R
p : A[X]
⊢ (r • p).toFinsupp = (C ((algebraMap R A) r) * p).toFinsupp

Tactic:
toFinsupp_smul,

Goal state after:
R : Type u
S : Type v
T : Type w
A : Type z
A' : Type u_1
B : Type u_2
a b : R
n : ℕ
inst✝⁴ : CommSemiring R
inst✝³ : Semiring A
inst✝² : Semiring B
inst✝¹ : Algebra R A
inst✝ : Algebra R B
p✝ q r✝ : R[X]
r : R
p : A[X]
⊢ r • p.toFinsupp = (C ((algebraMap R A) r) * p).toFinsupp
Module: Mathlib.Algebra.Polynomial.AlgebraMap

Goal state before:
pp: case monomial
R : Type u
A : Type z
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Algebra R A
x : A
n : ℕ
c : R
⊢ (aeval (MulOpposite.op x)) ((monomial n) c) = MulOpposite.op ((aeval x) ((monomial n) c))

Tactic:
simp [aeval_monomial, MulOpposite.op_pow, Algebra.commutes]

Goal state after:
Module: Mathlib.Order.PiLex

Goal state before:
pp: ι : Type u_1
β : ι → Type u_2
inst✝² : LinearOrder ι
x : (i : ι) → β i
i : ι
a : β i
inst✝¹ : (i : ι) → PartialOrder (β i)
inst✝ : WellFoundedLT ι
⊢ a < x i ∨ update x i a = x ↔ a < x i ∨ a = x i

Tactic:
update_eq_self_iff

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Basic

Goal state before:
pp: case single_add
R : Type u
σ : Type u_1
inst✝ : CommSemiring R
motive : MvPolynomial σ R → Prop
C : ∀ (a : R), motive (MvPolynomial.C a)
mul_X : ∀ (p : MvPolynomial σ R) (n : σ), motive p → motive (p * X n)
s : σ →₀ ℕ
a : R
n : σ
e : ℕ
p : σ →₀ ℕ
_hpn : n ∉ p.support
_he : e ≠ 0
ih : motive ((monomial p) a)
⊢ motive ((monomial (Finsupp.single n e + p)) a)

Tactic:
have : ∀ e : ℕ, motive (monomial p a * X n ^ e) := by
      intro e
      induction e with
      | zero => simp [ih]
      | succ e e_ih => simp [pow_succ, (mul_assoc _ _ _).symm, mul_X, e_ih]

Goal state after:
case single_add
R : Type u
σ : Type u_1
inst✝ : CommSemiring R
motive : MvPolynomial σ R → Prop
C : ∀ (a : R), motive (MvPolynomial.C a)
mul_X : ∀ (p : MvPolynomial σ R) (n : σ), motive p → motive (p * X n)
s : σ →₀ ℕ
a : R
n : σ
e : ℕ
p : σ →₀ ℕ
_hpn : n ∉ p.support
_he : e ≠ 0
ih : motive ((monomial p) a)
this : ∀ (e : ℕ), motive ((monomial p) a * X n ^ e)
⊢ motive ((monomial (Finsupp.single n e + p)) a)
Module: Mathlib.Algebra.MvPolynomial.Basic

Goal state before:
pp: R : Type u
σ : Type u_1
inst✝¹ : CommSemiring R
inst✝ : IsEmpty σ
p : MvPolynomial σ R
⊢ p = C (coeff 0 p)

Tactic:
obtain ⟨x, rfl⟩ := C_surjective σ p

Goal state after:
R : Type u
σ : Type u_1
inst✝¹ : CommSemiring R
inst✝ : IsEmpty σ
x : R
⊢ C x = C (coeff 0 (C x))
Module: Mathlib.Algebra.MvPolynomial.Basic

Goal state before:
pp: case mp
R : Type u
σ : Type u_1
inst✝ : CommSemiring R
r : R
φ : MvPolynomial σ R
c : σ →₀ ℕ
⊢ r ∣ r * coeff c φ

Tactic:
apply dvd_mul_right

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Degrees

Goal state before:
pp: R : Type u
σ : Type u_1
inst✝ : CommSemiring R
p : MvPolynomial σ R
n : ℕ
⊢ (p ^ n).degrees ≤ n • p.degrees

Tactic:
by
  simpa using degrees_prod_le (s := .range n) (f := fun _ ↦ p)

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Rename

Goal state before:
pp: case C
σ : Type u_1
R : Type u_4
inst✝ : CommSemiring R
p : MvPolynomial σ R
r : R
⊢ ∃ s q, C r = (rename Subtype.val) q

Tactic:
exact ⟨∅, C r, by rw [rename_C]⟩

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Degrees

Goal state before:
pp: case inr
R : Type u
σ : Type u_1
inst✝ : CommSemiring R
p q : MvPolynomial σ R
h : ∀ a ∈ p.degrees, ∀ b ∈ q.degrees, a ≠ b
d : σ →₀ ℕ
hd : d ∈ p.support
h0 : d ≠ 0
⊢ coeff d p + coeff d q ≠ 0

Tactic:
suffices q.coeff d = 0 by rwa [this, add_zero, coeff, ← Finsupp.mem_support_iff]

Goal state after:
case inr
R : Type u
σ : Type u_1
inst✝ : CommSemiring R
p q : MvPolynomial σ R
h : ∀ a ∈ p.degrees, ∀ b ∈ q.degrees, a ≠ b
d : σ →₀ ℕ
hd : d ∈ p.support
h0 : d ≠ 0
⊢ coeff d q = 0
Module: Mathlib.Algebra.MvPolynomial.Basic

Goal state before:
pp: R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Algebra R S
n : ℕ
x✝ : n + 2 ≠ 0
M : Submodule R S
⊢ coeffsIn σ (M ^ (n + 1)) * coeffsIn σ M = coeffsIn σ M ^ (n + 2)

Tactic:
coeffsIn_pow,

Goal state after:
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Algebra R S
n : ℕ
x✝ : n + 2 ≠ 0
M : Submodule R S
⊢ coeffsIn σ M ^ (n + 1) * coeffsIn σ M = coeffsIn σ M ^ (n + 2)

case a
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Algebra R S
n : ℕ
x✝ : n + 2 ≠ 0
M : Submodule R S
⊢ n + 1 ≠ 0
Module: Mathlib.Algebra.MvPolynomial.Degrees

Goal state before:
pp: R : Type u
σ : Type u_1
inst✝ : CommSemiring R
p q : MvPolynomial σ R
h : q.totalDegree < p.totalDegree
⊢ (p + q).totalDegree = p.totalDegree

Tactic:
apply le_antisymm
    · rw [← max_eq_left_of_lt h]
      exact totalDegree_add p q
    by_cases hp : p = 0
    · simp [hp]
    obtain ⟨b, hb₁, hb₂⟩ :=
      p.support.exists_mem_eq_sup (by simpa) fun m : σ →₀ ℕ => Multiset.card (toMultiset m)
    have hb : b ∉ q.support := by
      contrapose! h
      rw [totalDegree_eq p, hb₂, totalDegree_eq]
      apply Finset.le_sup h
    have hbb : b ∈ (p + q).support := by
      apply support_sdiff_support_subset_support_add
      rw [Finset.mem_sdiff]
      exact ⟨hb₁, hb⟩
    rw [totalDegree_eq, hb₂, totalDegree_eq]
    exact Finset.le_sup (f := fun m => Multiset.card (Finsupp.toMultiset m)) hbb

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Degrees

Goal state before:
pp: R : Type u
σ : Type u_1
inst✝ : CommSemiring R
ι : Type u_3
s : Finset ι
f : ι → MvPolynomial σ R
⊢ (s.sum f).totalDegree ≤ s.sup fun i ↦ (f i).totalDegree

Tactic:
induction s using Finset.cons_induction with

Goal state after:
Module: Mathlib.Algebra.Polynomial.Degree.TrailingDegree

Goal state before:
pp: case mp
R : Type u
inst✝ : Semiring R
p : R[X]
h : p.coeff p.natTrailingDegree = 0
hp : ¬p = 0
n : ℕ
hpn : ¬p.coeff n = 0
hn : ↑n = p.support.min
⊢ False

Tactic:
obtain rfl := (trailingDegree_eq_iff_natTrailingDegree_eq hp).1 hn.symm

Goal state after:
case mp
R : Type u
inst✝ : Semiring R
p : R[X]
h : p.coeff p.natTrailingDegree = 0
hp : ¬p = 0
hpn : ¬p.coeff p.natTrailingDegree = 0
hn : ↑p.natTrailingDegree = p.support.min
⊢ False
Module: Mathlib.Algebra.Polynomial.Degree.Lemmas

Goal state before:
pp: R : Type u
inst✝ : Semiring R
n : ℕ
p q : R[X]
qn : q.natDegree ≤ n
⊢ (p + q).natDegree ≤ n ↔ p.natDegree ≤ n

Tactic:
refine ⟨fun h => ?_, fun h => natDegree_add_le_of_degree_le h qn⟩
  refine natDegree_le_iff_coeff_eq_zero.mpr fun m hm => ?_
  convert! natDegree_le_iff_coeff_eq_zero.mp h m hm using 1
  rw [coeff_add, natDegree_le_iff_coeff_eq_zero.mp qn _ hm, add_zero]

Goal state after:
Module: Mathlib.Algebra.Polynomial.Reverse

Goal state before:
pp: N O n o : ℕ
hn : n ≤ N
ho : o ≤ O
⊢ (revAt (N + O)) (n + o) = (revAt N) n + (revAt O) o

Tactic:
by
  rcases Nat.le.dest hn with ⟨n', rfl⟩
  rcases Nat.le.dest ho with ⟨o', rfl⟩
  repeat' rw [revAt_le (le_add_right rfl.le)]
  rw [add_assoc, add_left_comm n' o, ← add_assoc, revAt_le (le_add_right rfl.le)]
  repeat' rw [add_tsub_cancel_left]

Goal state after:
Module: Mathlib.Algebra.Polynomial.Degree.Lemmas

Goal state before:
pp: case pos
R : Type u
S : Type v
inst✝ : Semiring R
f : S → R[X]
s : Finset S
h : {i | i ∈ s ∧ f i ≠ 0}.Pairwise (Ne on natDegree ∘ f)
x : S
hx : x ∈ s
hx' : f x ≠ 0
hs : s.Nonempty
⊢ (s.sup' hs fun i ↦ (f i).degree) = ↑(s.sup' hs fun i ↦ (f i).natDegree)

Tactic:
Finset.coe_sup' hs,

Goal state after:
case pos
R : Type u
S : Type v
inst✝ : Semiring R
f : S → R[X]
s : Finset S
h : {i | i ∈ s ∧ f i ≠ 0}.Pairwise (Ne on natDegree ∘ f)
x : S
hx : x ∈ s
hx' : f x ≠ 0
hs : s.Nonempty
⊢ (s.sup' hs fun i ↦ (f i).degree) = s.sup (WithBot.some ∘ fun i ↦ (f i).natDegree)
Module: Mathlib.Algebra.Polynomial.EraseLead

Goal state before:
pp: R : Type u_2
inst✝² : Ring R
inst✝¹ : NoZeroDivisors R
inst✝ : Nontrivial R
x : R
P : R[X]
hx : x ≠ 0
h : P.nextCoeff = 0
hp : ¬P = 0
he : P.eraseLead = 0
he₂ : ¬((X - C x) * P).eraseLead = 0
⊢ #(X - C x).support = 2

Tactic:
simpa [← sub_eq_add_neg] using!
        card_support_binomial one_ne_zero one_ne_zero (neg_ne_zero.mpr hx)

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Equiv

Goal state before:
pp: case monomial
σ : Type u_1
R : Type u_2
S : Type u_3
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Unique σ
φ : R →+* S
a : σ → S
d : σ →₀ ℕ
r : R
⊢ a default ^ 0 = 1

Tactic:
simp only [pow_zero]

Goal state after:
Module: Mathlib.Algebra.MvPolynomial.Equiv

Goal state before:
pp: case h_add
R : Type u
S₁ : Type v
inst✝ : CommSemiring R
m : Option S₁ →₀ ℕ
r : R
o✝ : Option S₁
m₁✝ m₂✝ : ℕ
⊢ (o✝.elim Polynomial.X fun s ↦ Polynomial.C (X s)) ^ (m₁✝ + m₂✝) =
    (o✝.elim Polynomial.X fun s ↦ Polynomial.C (X s)) ^ m₁✝ * (o✝.elim Polynomial.X fun s ↦ Polynomial.C (X s)) ^ m₂✝

Tactic:
rw [pow_add]

Goal state after:
Module: Mathlib.Algebra.Polynomial.Monic

Goal state before:
pp: R : Type u
inst✝ : Semiring R
p : R[X]
hp : p.Monic
this : C (p.coeff p.natDegree) = 1
⊢ C (p.coeff p.natDegree) * X ^ p.natDegree + ∑ x ∈ range p.natDegree, C (p.coeff x) * X ^ x =
    X ^ p.natDegree + ∑ i ∈ range p.natDegree, C (p.coeff i) * X ^ i

Tactic:
by rw [this, one_mul]

Goal state after:
Module: Mathlib.Algebra.Polynomial.Monic

Goal state before:
pp: R : Type u
inst✝ : Semiring R
p : R[X]
b : R
hp : b * p.leadingCoeff = 1
⊢ (C b * p).leadingCoeff = 1

Tactic:
nontriviality

Goal state after:
R : Type u
inst✝ : Semiring R
p : R[X]
b : R
hp : b * p.leadingCoeff = 1
a✝ : Nontrivial R
⊢ (C b * p).leadingCoeff = 1
Module: Mathlib.Algebra.Polynomial.Monic

Goal state before:
pp: R : Type u
inst✝ : Semiring R
p : R[X]
b : R
hp : p.leadingCoeff * b = 1
⊢ (p * C b).leadingCoeff = 1

Tactic:
nontriviality

Goal state after:
R : Type u
inst✝ : Semiring R
p : R[X]
b : R
hp : p.leadingCoeff * b = 1
a✝ : Nontrivial R
⊢ (p * C b).leadingCoeff = 1
Module: Mathlib.Algebra.Polynomial.Monic

Goal state before:
pp: R : Type u
inst✝ : Semiring R
p q : R[X]
hp : p.Monic
hq : q.Monic
h : q.natDegree ≠ 0
a✝ : Nontrivial R
⊢ (p.comp q).Monic

Tactic:
have : (p.comp q).natDegree = p.natDegree * q.natDegree :=
    natDegree_comp_eq_of_mul_ne_zero <| by simp [hp.leadingCoeff, hq.leadingCoeff]

Goal state after:
R : Type u
inst✝ : Semiring R
p q : R[X]
hp : p.Monic
hq : q.Monic
h : q.natDegree ≠ 0
a✝ : Nontrivial R
this : (p.comp q).natDegree = p.natDegree * q.natDegree
⊢ (p.comp q).Monic
Module: Mathlib.Algebra.Polynomial.Monic

Goal state before:
pp: R : Type u
inst✝ : Semiring R
p q : R[X]
hp : p.Monic
hq : q.Monic
⊢ (p * q).nextCoeff = p.nextCoeff + q.nextCoeff

Tactic:
nontriviality

Goal state after:
R : Type u
inst✝ : Semiring R
p q : R[X]
hp : p.Monic
hq : q.Monic
a✝ : Nontrivial R
⊢ (p * q).nextCoeff = p.nextCoeff + q.nextCoeff
Module: Mathlib.Algebra.Polynomial.Monic

Goal state before:
pp: R : Type u
inst✝ : Semiring R
p : R[X]
hm : p.Monic
hpu : IsUnit p
a✝ : Nontrivial R
q : R[X]
h : p * q = 1
this : (p * q).natDegree = p.natDegree + q.natDegree
⊢ p = 1

Tactic:
rw [h, natDegree_one, eq_comm, add_eq_zero] at this

Goal state after:
R : Type u
inst✝ : Semiring R
p : R[X]
hm : p.Monic
hpu : IsUnit p
a✝ : Nontrivial R
q : R[X]
h : p * q = 1
this : p.natDegree = 0 ∧ q.natDegree = 0
⊢ p = 1
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: R : Type u
inst✝ : Ring R
p : R[X]
⊢ p.restriction.natDegree = p.natDegree

Tactic:
simp [natDegree]

Goal state after:
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: R : Type u
inst✝ : CommSemiring R
I : Ideal R[X]
x : R
x✝ : ∃ p ∈ I, p.degree ≤ ↑0 ∧ p.leadingCoeff = x
p : R[X]
hpI : p ∈ I
hpdeg : p.degree ≤ ↑0
hpx : p.leadingCoeff = x
⊢ C (p.coeff 0) ∈ I

Tactic:
← eq_C_of_degree_le_zero hpdeg

Goal state after:
R : Type u
inst✝ : CommSemiring R
I : Ideal R[X]
x : R
x✝ : ∃ p ∈ I, p.degree ≤ ↑0 ∧ p.leadingCoeff = x
p : R[X]
hpI : p ∈ I
hpdeg : p.degree ≤ ↑0
hpx : p.leadingCoeff = x
⊢ p ∈ I
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: case insert
R : Type u
inst✝ : CommSemiring R
ι : Type u_2
f : ι → R[X]
I : Ideal R
n : ι → ℕ
a : ι
s : Finset ι
ha : a ∉ s
hs : (∀ i ∈ s, ∀ (k : ℕ), (f i).coeff k ∈ I ^ (n i - k)) → ∀ (k : ℕ), (s.prod f).coeff k ∈ I ^ (s.sum n - k)
h : ∀ i ∈ insert a s, ∀ (k : ℕ), (f i).coeff k ∈ I ^ (n i - k)
i j : ℕ
e : (i, j) ∈ antidiagonal (i + j)
⊢ (f a).coeff (i, j).1 * (∏ x ∈ s, f x).coeff (i, j).2 ∈ I ^ (n a - i + (∑ x ∈ s, n x - j))

Tactic:
rw [pow_add]

Goal state after:
case insert
R : Type u
inst✝ : CommSemiring R
ι : Type u_2
f : ι → R[X]
I : Ideal R
n : ι → ℕ
a : ι
s : Finset ι
ha : a ∉ s
hs : (∀ i ∈ s, ∀ (k : ℕ), (f i).coeff k ∈ I ^ (n i - k)) → ∀ (k : ℕ), (s.prod f).coeff k ∈ I ^ (s.sum n - k)
h : ∀ i ∈ insert a s, ∀ (k : ℕ), (f i).coeff k ∈ I ^ (n i - k)
i j : ℕ
e : (i, j) ∈ antidiagonal (i + j)
⊢ (f a).coeff (i, j).1 * (∏ x ∈ s, f x).coeff (i, j).2 ∈ I ^ (n a - i) * I ^ (∑ x ∈ s, n x - j)
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: case inr
R : Type u
inst✝ : CommRing R
P : Ideal R
h : P.IsPrime
f g : R[X]
hf : ∃ n, f.coeff n ∉ P
hg : ∃ n, g.coeff n ∉ P
m : ℕ := ⋯
n : ℕ := ⋯
i j : ℕ
hij : (¬i = m ∨ ¬j = n) ∧ i + j = m + n
hj : j < n
⊢ g.coeff (i, j).2 ∈ P

Tactic:
exact Classical.not_not.1 (Nat.find_min hg hj)

Goal state after:
Module: Mathlib.Algebra.Algebra.Subalgebra.IsSimpleOrder

Goal state before:
pp: F : Type u_1
A : Type u_2
inst✝³ : Field F
inst✝² : Ring A
inst✝¹ : IsDomain A
inst✝ : Algebra F A
hp : Nat.Prime (finrank F A)
K : Subalgebra F A
this : FiniteDimensional F A
⊢ K = ⊥ ∨ K = ⊤

Tactic:
let := divisionRingOfFiniteDimensional F K

Goal state after:
F : Type u_1
A : Type u_2
inst✝³ : Field F
inst✝² : Ring A
inst✝¹ : IsDomain A
inst✝ : Algebra F A
hp : Nat.Prime (finrank F A)
K : Subalgebra F A
this✝ : FiniteDimensional F A
this : DivisionRing ↥K := divisionRingOfFiniteDimensional F ↥K
⊢ K = ⊥ ∨ K = ⊤
Module: Mathlib.RingTheory.FiniteType

Goal state before:
pp: R : Type uR
A : Type uA
B : Type uB
inst✝⁵ : CommSemiring R
inst✝⁴ : Semiring A
inst✝³ : Semiring B
inst✝² : Algebra R A
inst✝¹ : Algebra R B
inst✝ : FiniteType R A
f : A →ₐ[R] B
hf : Surjective ⇑f
⊢ ⊤.FG

Tactic:
convert ‹FiniteType R A›.1.map f

Goal state after:
R : Type uR
A : Type uA
B : Type uB
inst✝⁵ : CommSemiring R
inst✝⁴ : Semiring A
inst✝³ : Semiring B
inst✝² : Algebra R A
inst✝¹ : Algebra R B
inst✝ : FiniteType R A
f : A →ₐ[R] B
hf : Surjective ⇑f
⊢ ⊤ = Subalgebra.map f ⊤
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: case h.inr
R : Type u
inst✝ : CommRing R
inst : IsNoetherianRing R
I : Ideal R[X]
M : Submodule R R := ⋯.min (Set.range I.leadingCoeffNth) ⋯
hm : M ∈ Set.range I.leadingCoeffNth
N : ℕ
HN : I.leadingCoeffNth N = M
s : Finset R[X]
hs : Submodule.span R ↑s = I.degreeLE ↑N
hm2 : ∀ (k : ℕ), I.leadingCoeffNth k ≤ M
hs2 : ∀ {x : R[X]}, x ∈ I.degreeLE ↑N → x ∈ Ideal.span ↑s
this : Submodule.span R[X] ↑s = Ideal.span ↑s
k : ℕ
ih : ∀ m < k, ∀ ⦃p : R[X]⦄, p ∈ I → p.natDegree = m → p ∈ Ideal.span ↑s
p : R[X]
hp : p ∈ I
hn : p.natDegree = k
h : N < k
hp0 : p ≠ 0
⊢ p ∈ Ideal.span ↑s

Tactic:
have : (0 : R) ≠ 1 := by
            intro h
            apply hp0
            ext i
            refine (mul_one _).symm.trans ?_
            rw [← h, mul_zero]
            rfl

Goal state after:
case h.inr
R : Type u
inst✝ : CommRing R
inst : IsNoetherianRing R
I : Ideal R[X]
M : Submodule R R := ⋯.min (Set.range I.leadingCoeffNth) ⋯
hm : M ∈ Set.range I.leadingCoeffNth
N : ℕ
HN : I.leadingCoeffNth N = M
s : Finset R[X]
hs : Submodule.span R ↑s = I.degreeLE ↑N
hm2 : ∀ (k : ℕ), I.leadingCoeffNth k ≤ M
hs2 : ∀ {x : R[X]}, x ∈ I.degreeLE ↑N → x ∈ Ideal.span ↑s
this✝ : Submodule.span R[X] ↑s = Ideal.span ↑s
k : ℕ
ih : ∀ m < k, ∀ ⦃p : R[X]⦄, p ∈ I → p.natDegree = m → p ∈ Ideal.span ↑s
p : R[X]
hp : p ∈ I
hn : p.natDegree = k
h : N < k
hp0 : p ≠ 0
this : 0 ≠ 1
⊢ p ∈ Ideal.span ↑s
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: case h.inr
R : Type u
inst✝ : CommRing R
inst : IsNoetherianRing R
I : Ideal R[X]
M : Submodule R R := ⋯.min (Set.range I.leadingCoeffNth) ⋯
hm : M ∈ Set.range I.leadingCoeffNth
N : ℕ
HN : I.leadingCoeffNth N = M
s : Finset R[X]
hs : Submodule.span R ↑s = I.degreeLE ↑N
hm2 : ∀ (k : ℕ), I.leadingCoeffNth k ≤ M
hs2 : ∀ {x : R[X]}, x ∈ I.degreeLE ↑N → x ∈ Ideal.span ↑s
this✝² : Submodule.span R[X] ↑s = Ideal.span ↑s
k : ℕ
ih : ∀ m < k, ∀ ⦃p : R[X]⦄, p ∈ I → p.natDegree = m → p ∈ Ideal.span ↑s
p : R[X]
hp : p ∈ I
hn : p.natDegree = k
h : N < k
hp0 : p ≠ 0
this✝¹ : 0 ≠ 1
this✝ : Nontrivial R
q : R[X]
hq : q ∈ I
hdq : q.degree ≤ ↑N
hlqp : q.leadingCoeff = p.leadingCoeff
hq0 : q ≠ 0
h1 : p.degree = (q * X ^ (k - q.natDegree)).degree
h2 : p.leadingCoeff = (q * X ^ (k - q.natDegree)).leadingCoeff
this : (p - q * X ^ (k - q.natDegree)).degree < ↑p.natDegree
⊢ p ∈ Ideal.span ↑s

Tactic:
← sub_add_cancel p (q * Polynomial.X ^ (k - q.natDegree))

Goal state after:
case h.inr
R : Type u
inst✝ : CommRing R
inst : IsNoetherianRing R
I : Ideal R[X]
M : Submodule R R := ⋯.min (Set.range I.leadingCoeffNth) ⋯
hm : M ∈ Set.range I.leadingCoeffNth
N : ℕ
HN : I.leadingCoeffNth N = M
s : Finset R[X]
hs : Submodule.span R ↑s = I.degreeLE ↑N
hm2 : ∀ (k : ℕ), I.leadingCoeffNth k ≤ M
hs2 : ∀ {x : R[X]}, x ∈ I.degreeLE ↑N → x ∈ Ideal.span ↑s
this✝² : Submodule.span R[X] ↑s = Ideal.span ↑s
k : ℕ
ih : ∀ m < k, ∀ ⦃p : R[X]⦄, p ∈ I → p.natDegree = m → p ∈ Ideal.span ↑s
p : R[X]
hp : p ∈ I
hn : p.natDegree = k
h : N < k
hp0 : p ≠ 0
this✝¹ : 0 ≠ 1
this✝ : Nontrivial R
q : R[X]
hq : q ∈ I
hdq : q.degree ≤ ↑N
hlqp : q.leadingCoeff = p.leadingCoeff
hq0 : q ≠ 0
h1 : p.degree = (q * X ^ (k - q.natDegree)).degree
h2 : p.leadingCoeff = (q * X ^ (k - q.natDegree)).leadingCoeff
this : (p - q * X ^ (k - q.natDegree)).degree < ↑p.natDegree
⊢ p - q * X ^ (k - q.natDegree) + q * X ^ (k - q.natDegree) ∈ Ideal.span ↑s
Module: Mathlib.Algebra.Algebra.Subalgebra.Pointwise

Goal state before:
pp: case refine_1.inr
R : Type u_3
A : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring A
inst✝ : Algebra R A
S T : Subalgebra R A
x✝ : A
hx : x✝ ∈ Algebra.adjoin R (↑S ∪ ↑T)
x : A
hxT : x ∈ ↑T
⊢ x ∈ toSubmodule S * toSubmodule T

Tactic:
· rw [← one_mul x]
      exact Submodule.mul_mem_mul (show (1 : A) ∈ S from one_mem S) hxT

Goal state after:
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: σ : Type v
R : Type u_2
inst✝ : CommSemiring R
m n : ℕ
F : MvPolynomial σ R
hF : F.totalDegree ≤ m
f : σ → R[X]
hf : ∀ (i : σ), (f i).natDegree ≤ n
d : σ →₀ ℕ
hd : d ∈ F.coeff.support
this : ∑ i ∈ d.support, d i * n ≤ m * n
i : σ
⊢ d i * (f i).natDegree ≤ d i * n

Tactic:
exact mul_le_mul' le_rfl (hf i)

Goal state after:
Module: Mathlib.RingTheory.Polynomial.Basic

Goal state before:
pp: R : Type u
σ : Type v
inst✝ : CommRing R
I : Ideal R
f : MvPolynomial σ R
⊢ f ∈ Ideal.map C I ↔ ∀ (m : σ →₀ ℕ), coeff m f ∈ I

Tactic:
classical
  constructor
  · intro hf
    refine Submodule.span_induction ?_ ?_ ?_ ?_ hf
    · intro f hf n
      obtain ⟨x, hx⟩ := (Set.mem_image _ _ _).mp hf
      rw [← hx.right, coeff_C]
      by_cases h : n = 0
      · simpa [h] using hx.left
      · simp [Ne.symm h]
    · simp
    · exact fun f g _ _ hf hg n => by simp [I.add_mem (hf n) (hg n)]
    · intro f g _ hg n
      rw [smul_eq_mul, coeff_mul]
      exact I.sum_mem fun c _ => I.mul_mem_left (f.coeff c.fst) (hg c.snd)
  · intro hf
    rw [as_sum f]
    suffices ∀ m ∈ f.support, monomial m (coeff m f) ∈ (Ideal.map C I : Ideal (MvPolynomial σ R)) by
      exact Submodule.sum_mem _ this
    intro m _
    rw [← mul_one (coeff m f), ← C_mul_monomial]
    suffices C (coeff m f) ∈ (Ideal.map C I : Ideal (MvPolynomial σ R)) by
      exact Ideal.mul_mem_right _ _ this
    apply Ideal.mem_map_of_mem _
    exact hf m

Goal state after:
Module: Mathlib.Data.Int.ModEq

Goal state before:
pp: n a b : ℤ
⊢ a ≡ b - n [ZMOD n] ↔ a ≡ b [ZMOD n]

Tactic:
rw [← modEq_add_modulus_iff, sub_add_cancel]

Goal state after:
Module: Mathlib.Data.Int.ModEq

Goal state before:
pp: case e'_2
a b m n : ℤ
hmn : m.natAbs.Coprime n.natAbs
⊢ a ≡ b [ZMOD ↑(m.lcm n)] ↔ a ≡ b [ZMOD m * n]

Tactic:
rw [lcm_eq_mul_iff.mpr (.inr <| .inr hmn), ← natAbs_mul, modEq_natAbs]

Goal state after:
Module: Mathlib.Algebra.CharP.Basic

Goal state before:
pp: case inr.inl.inr.inr
R : Type u_2
inst✝¹ : NonAssocRing R
inst✝ : Nontrivial R
hR : ringChar R ≠ 2
h : 1 = -1
⊢ 1 = -1

Tactic:
exact ((Ring.neg_one_ne_one_of_char_ne_two hR).symm h).elim

Goal state after:
Module: Mathlib.RingTheory.Ideal.Quotient.Operations

Goal state before:
pp: case intro
R : Type u_2
inst✝¹ : CommRing R
ι : Type u_3
inst✝ : Finite ι
I : ι → Ideal R
hI : Pairwise (IsCoprime on I)
val✝ : Fintype ι
g : (i : ι) → R ⧸ I i
f : ι → R
hf : ∀ (i : ι), (Quotient.mk (I i)) (f i) = g i
key : ∀ (i : ι), ∃ e, (Quotient.mk (I i)) e = 1 ∧ ∀ (j : ι), j ≠ i → (Quotient.mk (I j)) e = 0
⊢ ∃ a, (quotientInfToPiQuotient I) a = g

Tactic:
choose e he using key

Goal state after:
case intro
R : Type u_2
inst✝¹ : CommRing R
ι : Type u_3
inst✝ : Finite ι
I : ι → Ideal R
hI : Pairwise (IsCoprime on I)
val✝ : Fintype ι
g : (i : ι) → R ⧸ I i
f : ι → R
hf : ∀ (i : ι), (Quotient.mk (I i)) (f i) = g i
e : ι → R
he : ∀ (i : ι), (Quotient.mk (I i)) (e i) = 1 ∧ ∀ (j : ι), j ≠ i → (Quotient.mk (I j)) (e i) = 0
⊢ ∃ a, (quotientInfToPiQuotient I) a = g
Module: Mathlib.Dynamics.PeriodicPts.Defs

Goal state before:
pp: α : Type u_1
f : α → α
x : α
m n : ℕ
hx : x ∈ periodicPts f
hm : IsPeriodicPt f m (f^[n] x)
⊢ IsPeriodicPt f m x

Tactic:
rcases hx with ⟨r, hr, hr'⟩
  suffices n ≤ (n / r + 1) * r by
    unfold IsPeriodicPt IsFixedPt
    convert! (hm.apply_iterate ((n / r + 1) * r - n)).eq <;>
      rw [← iterate_add_apply, Nat.sub_add_cancel this, iterate_mul, (hr'.iterate _).eq]
  rw [Nat.add_mul, one_mul]
  exact (Nat.lt_div_mul_add hr).le

Goal state after:
Module: Mathlib.Algebra.Star.Subalgebra

Goal state before:
pp: R : Type u_2
A : Type u_3
inst✝⁵ : CommSemiring R
inst✝⁴ : StarRing R
inst✝³ : Semiring A
inst✝² : Algebra R A
inst✝¹ : StarRing A
inst✝ : StarModule R A
s : Set A
⊢ Algebra.adjoin R (s ∪ star s) ≤ Subalgebra.centralizer R (↑(centralizer R s) ∪ star ↑(centralizer R s))

Tactic:
convert! Algebra.adjoin_le_centralizer_centralizer R (s ∪ star s)

Goal state after:
R : Type u_2
A : Type u_3
inst✝⁵ : CommSemiring R
inst✝⁴ : StarRing R
inst✝³ : Semiring A
inst✝² : Algebra R A
inst✝¹ : StarRing A
inst✝ : StarModule R A
s : Set A
⊢ ↑(centralizer R s) ∪ star ↑(centralizer R s) = ↑(Subalgebra.centralizer R (s ∪ star s))
Module: Mathlib.Algebra.Star.Subalgebra

Goal state before:
pp: R : Type u_2
A : Type u_3
inst✝⁵ : CommSemiring R
inst✝⁴ : StarRing R
inst✝³ : Semiring A
inst✝² : Algebra R A
inst✝¹ : StarRing A
inst✝ : StarModule R A
s : Set A
hcomm : ∀ x ∈ s, ∀ y ∈ s, x * y = y * x
hcomm_star : ∀ a ∈ s, ∀ b ∈ s, a * star b = star b * a
⊢ IsMulCommutative ↥(adjoin R s)

Tactic:
have := adjoin_le_centralizer_centralizer R s
  refine .of_setLike_mul_comm fun _ h₁ _ h₂ ↦ ?_
  have hcomm : ∀ a ∈ s ∪ star s, ∀ b ∈ s ∪ star s, a * b = b * a := fun a ha b hb ↦
    Set.union_star_self_comm (fun _ ha _ hb ↦ hcomm _ hb _ ha)
      (fun _ ha _ hb ↦ hcomm_star _ hb _ ha) b hb a ha
  apply this at h₁
  apply this at h₂
  rw [← SetLike.mem_coe, coe_centralizer_centralizer] at h₁ h₂
  exact Set.centralizer_centralizer_comm_of_comm hcomm _ h₁ _ h₂

Goal state after:
Module: Mathlib.Data.List.Permutation

Goal state before:
pp: α : Type u_1
s : List α
x : α
⊢ (permutations'Aux x s).length = s.length + 1

Tactic:
induction s with

Goal state after: