mathlib-initiative/mathlib-tactics huggingface dataset:
Module: Mathlib.RingTheory.LocalRing.Length

Goal state before:
pp: case pos
A : Type u_1
B : Type u_2
M : Type u_3
inst✝⁹ : CommRing A
inst✝⁸ : CommRing B
inst✝⁷ : IsLocalRing A
inst✝⁶ : IsLocalRing B
inst✝⁵ : Algebra A B
inst✝⁴ : IsLocalHom (algebraMap A B)
inst✝³ : AddCommGroup M
inst✝² : Module A M
inst✝¹ : Module B M
inst✝ : IsScalarTower A B M
h : IsFiniteLength B M
⊢ length A M = length B M * length (ResidueField A) (ResidueField B)

Tactic:
obtain ⟨s, hs_bot, hs_top⟩ := isFiniteLength_iff_exists_compositionSeries.mp h

Goal state after:
case pos
A : Type u_1
B : Type u_2
M : Type u_3
inst✝⁹ : CommRing A
inst✝⁸ : CommRing B
inst✝⁷ : IsLocalRing A
inst✝⁶ : IsLocalRing B
inst✝⁵ : Algebra A B
inst✝⁴ : IsLocalHom (algebraMap A B)
inst✝³ : AddCommGroup M
inst✝² : Module A M
inst✝¹ : Module B M
inst✝ : IsScalarTower A B M
h : IsFiniteLength B M
s : CompositionSeries (Submodule B M)
hs_bot : RelSeries.head s = ⊥
hs_top : RelSeries.last s = ⊤
⊢ length A M = length B M * length (ResidueField A) (ResidueField B)
Module: Mathlib.RingTheory.LocalRing.Length

Goal state before:
pp: case pos
A : Type u_1
B : Type u_2
M : Type u_3
inst✝⁸ : CommRing A
inst✝⁷ : CommRing B
inst✝⁶ : IsLocalRing A
inst✝⁵ : IsLocalRing B
inst✝⁴ : Algebra A B
inst✝³ : IsLocalHom (algebraMap A B)
inst✝² : AddCommGroup M
inst✝¹ : Module A M
inst✝ : Flat A B
h : IsFiniteLength A M
⊢ length B (B ⊗[A] M) = length A M * length B (B ⧸ Ideal.map (algebraMap A B) (maximalIdeal A))

Tactic:
obtain ⟨s, hs_bot, hs_top⟩ := isFiniteLength_iff_exists_compositionSeries.mp h

Goal state after:
case pos
A : Type u_1
B : Type u_2
M : Type u_3
inst✝⁸ : CommRing A
inst✝⁷ : CommRing B
inst✝⁶ : IsLocalRing A
inst✝⁵ : IsLocalRing B
inst✝⁴ : Algebra A B
inst✝³ : IsLocalHom (algebraMap A B)
inst✝² : AddCommGroup M
inst✝¹ : Module A M
inst✝ : Flat A B
h : IsFiniteLength A M
s : CompositionSeries (Submodule A M)
hs_bot : RelSeries.head s = ⊥
hs_top : RelSeries.last s = ⊤
⊢ length B (B ⊗[A] M) = length A M * length B (B ⧸ Ideal.map (algebraMap A B) (maximalIdeal A))
Module: Mathlib.RingTheory.LocalRing.Length

Goal state before:
pp: case neg
A : Type u_1
B : Type u_2
M : Type u_3
inst✝⁸ : CommRing A
inst✝⁷ : CommRing B
inst✝⁶ : IsLocalRing A
inst✝⁵ : IsLocalRing B
inst✝⁴ : Algebra A B
inst✝³ : IsLocalHom (algebraMap A B)
inst✝² : AddCommGroup M
inst✝¹ : Module A M
inst✝ : Flat A B
h : ¬IsFiniteLength A M
⊢ length B (B ⊗[A] M) = length A M * length B (B ⧸ Ideal.map (algebraMap A B) (maximalIdeal A))

Tactic:
have : ¬ IsFiniteLength B (B ⊗[A] M) := by
      contrapose! h
      rw [isFiniteLength_iff_isNoetherian_isArtinian] at h ⊢
      have : FaithfullyFlat A B := FaithfullyFlat.of_flat_of_isLocalHom
      exact h.imp IsNoetherian.of_isNoetherian_tensorProduct_of_faithfullyFlat
        IsArtinian.of_isArtinian_tensorProduct_of_faithfullyFlat

Goal state after:
case neg
A : Type u_1
B : Type u_2
M : Type u_3
inst✝⁸ : CommRing A
inst✝⁷ : CommRing B
inst✝⁶ : IsLocalRing A
inst✝⁵ : IsLocalRing B
inst✝⁴ : Algebra A B
inst✝³ : IsLocalHom (algebraMap A B)
inst✝² : AddCommGroup M
inst✝¹ : Module A M
inst✝ : Flat A B
h : ¬IsFiniteLength A M
this : ¬IsFiniteLength B (B ⊗[A] M)
⊢ length B (B ⊗[A] M) = length A M * length B (B ⧸ Ideal.map (algebraMap A B) (maximalIdeal A))
Module: Mathlib.NumberTheory.RamificationInertia.Ramification

Goal state before:
pp: R : Type u
inst✝³ : CommRing R
S : Type v
inst✝² : CommRing S
inst✝¹ : Algebra R S
p : Ideal R
P : Ideal S
inst✝ : IsDedekindDomain S
hp0 : map f p ≠ ⊥
hP : P.IsPrime
hP0 : P ≠ ⊥
hPirr : Irreducible P
⊢ p.ramificationIdx' P = Multiset.count P (normalizedFactors (map f p))

Tactic:
refine ramificationIdx'_spec (Ideal.le_of_dvd ?_) (mt Ideal.dvd_iff_le.mpr ?_)

Goal state after:
case refine_1
R : Type u
inst✝³ : CommRing R
S : Type v
inst✝² : CommRing S
inst✝¹ : Algebra R S
p : Ideal R
P : Ideal S
inst✝ : IsDedekindDomain S
hp0 : map f p ≠ ⊥
hP : P.IsPrime
hP0 : P ≠ ⊥
hPirr : Irreducible P
⊢ P ^ Multiset.count P (normalizedFactors (map f p)) ∣ map f p

case refine_2
R : Type u
inst✝³ : CommRing R
S : Type v
inst✝² : CommRing S
inst✝¹ : Algebra R S
p : Ideal R
P : Ideal S
inst✝ : IsDedekindDomain S
hp0 : map f p ≠ ⊥
hP : P.IsPrime
hP0 : P ≠ ⊥
hPirr : Irreducible P
⊢ ¬P ^ (Multiset.count P (normalizedFactors (map f p)) + 1) ∣ map f p
Module: Mathlib.RingTheory.QuasiFinite.Basic

Goal state before:
pp: R : Type u_1
S : Type u_2
T : Type u_3
inst✝⁸ : CommRing R
inst✝⁷ : CommRing S
inst✝⁶ : CommRing T
inst✝⁵ : Algebra R S
inst✝⁴ : Algebra R T
inst✝³ : Algebra S T
inst✝² : IsScalarTower R S T
M : Submonoid S
inst✝¹ : IsLocalization M T
inst✝ : QuasiFinite R S
⊢ QuasiFinite S T

Tactic:
refine ⟨fun P hP ↦ .of_surjective (Algebra.linearMap P.ResidueField (P.Fiber T)) ?_⟩
    rw [← LinearMap.coe_restrictScalars (R := S), ← LinearMap.range_eq_top,
      ← top_le_iff, ← TensorProduct.span_tmul_eq_top, Submodule.span_le]
    rintro _ ⟨p, s, rfl⟩
    obtain ⟨s, t, rfl⟩ := IsLocalization.exists_mk'_eq M s
    use s • p / algebraMap _ _ t.1
    apply ((IsLocalization.map_units T t).map
      Algebra.TensorProduct.includeRight).mul_left_injective
    by_cases ht : algebraMap _ P.ResidueField t.1 = 0
    · simp [ht]
    trans (s • p) ⊗ₜ[S] 1
    · simp [div_mul_cancel₀ _ ht]
    · dsimp; simp [Algebra.algebraMap_eq_smul_one, smul_tmul]

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

Goal state before:
pp: R : Type u_1
S : Type u_2
T : Type u_3
inst✝⁹ : CommRing R
inst✝⁸ : CommRing S
inst✝⁷ : CommRing T
inst✝⁶ : Algebra R S
inst✝⁵ : Algebra R T
inst✝⁴ : Algebra S T
inst✝³ : IsScalarTower R S T
inst✝² : Algebra.IsIntegral R S
inst✝¹ : FiniteType R T
s : S
inst✝ : IsLocalization.Away s T
A : Subalgebra R S := R[s]
sA : ↥A := ⟨s, ⋯⟩
f : Localization.Away sA →+* T := IsLocalization.Away.lift sA ⋯
this✝⁶ : Algebra (Localization.Away sA) T := f.toAlgebra
this✝⁵ : Algebra (↥A) (Localization.Away sA) := OreLocalization.instAlgebra
this✝⁴ : SMul (↥A) (Localization.Away sA) := this✝⁵.toSMul
this✝³ : MulAction (↥A) (Localization.Away sA) := toModule.toMulAction
this✝² : IsScalarTower R (↥A) (Localization.Away sA)
this✝¹ : IsScalarTower (↥A) (Localization.Away sA) T
this✝ : IsScalarTower R (Localization.Away sA) T
x : S
n : ℕ
this : IsIntegral (Localization.Away sA) ((algebraMap S T) x)
⊢ IsLocalization.mk' T x ⟨(fun x ↦ s ^ x) n, ⋯⟩ = Localization.Away.invSelf sA ^ n • (algebraMap S T) x

Tactic:
IsLocalization.mk'_eq_iff_eq_mul

Goal state after:
R : Type u_1
S : Type u_2
T : Type u_3
inst✝⁹ : CommRing R
inst✝⁸ : CommRing S
inst✝⁷ : CommRing T
inst✝⁶ : Algebra R S
inst✝⁵ : Algebra R T
inst✝⁴ : Algebra S T
inst✝³ : IsScalarTower R S T
inst✝² : Algebra.IsIntegral R S
inst✝¹ : FiniteType R T
s : S
inst✝ : IsLocalization.Away s T
A : Subalgebra R S := R[s]
sA : ↥A := ⟨s, ⋯⟩
f : Localization.Away sA →+* T := IsLocalization.Away.lift sA ⋯
this✝⁶ : Algebra (Localization.Away sA) T := f.toAlgebra
this✝⁵ : Algebra (↥A) (Localization.Away sA) := OreLocalization.instAlgebra
this✝⁴ : SMul (↥A) (Localization.Away sA) := this✝⁵.toSMul
this✝³ : MulAction (↥A) (Localization.Away sA) := toModule.toMulAction
this✝² : IsScalarTower R (↥A) (Localization.Away sA)
this✝¹ : IsScalarTower (↥A) (Localization.Away sA) T
this✝ : IsScalarTower R (Localization.Away sA) T
x : S
n : ℕ
this : IsIntegral (Localization.Away sA) ((algebraMap S T) x)
⊢ (algebraMap S T) x = Localization.Away.invSelf sA ^ n • (algebraMap S T) x * (algebraMap S T) ↑⟨(fun x ↦ s ^ x) n, ⋯⟩
Module: Mathlib.RingTheory.QuasiFinite.Basic

Goal state before:
pp: R : Type u_1
S : Type u_2
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
inst✝⁵ : Algebra R S
p : Ideal S
inst✝⁴ : p.IsPrime
inst✝³ : QuasiFiniteAt R p
A : Type u_4
inst✝² : CommRing A
inst✝¹ : Algebra R A
q : Ideal (A ⊗[R] S)
inst✝ : q.IsPrime
hq : p = Ideal.comap TensorProduct.includeRight.toRingHom q
f : A ⊗[R] Localization.AtPrime p →ₐ[A] Localization.AtPrime q :=
  TensorProduct.lift (ofId A (Localization.AtPrime q))
    { toRingHom := Localization.localRingHom p q TensorProduct.includeRight.toRingHom hq, commutes' := ⋯ } ⋯
g : A ⊗[R] S →ₐ[A] A ⊗[R] Localization.AtPrime p :=
  TensorProduct.map (AlgHom.id A A) (IsScalarTower.toAlgHom R S (Localization.AtPrime p))
this : ∀ (x : A ⊗[R] S), f (g x) = (algebraMap (A ⊗[R] S) (Localization.AtPrime q)) x
x : Localization.AtPrime q
⊢ ∃ s, IsUnit (f s) ∧ x * f s ∈ f.range

Tactic:
obtain ⟨x, ⟨s, hs⟩, rfl⟩ := IsLocalization.exists_mk'_eq q.primeCompl x

Goal state after:
R : Type u_1
S : Type u_2
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
inst✝⁵ : Algebra R S
p : Ideal S
inst✝⁴ : p.IsPrime
inst✝³ : QuasiFiniteAt R p
A : Type u_4
inst✝² : CommRing A
inst✝¹ : Algebra R A
q : Ideal (A ⊗[R] S)
inst✝ : q.IsPrime
hq : p = Ideal.comap TensorProduct.includeRight.toRingHom q
f : A ⊗[R] Localization.AtPrime p →ₐ[A] Localization.AtPrime q :=
  TensorProduct.lift (ofId A (Localization.AtPrime q))
    { toRingHom := Localization.localRingHom p q TensorProduct.includeRight.toRingHom hq, commutes' := ⋯ } ⋯
g : A ⊗[R] S →ₐ[A] A ⊗[R] Localization.AtPrime p :=
  TensorProduct.map (AlgHom.id A A) (IsScalarTower.toAlgHom R S (Localization.AtPrime p))
this : ∀ (x : A ⊗[R] S), f (g x) = (algebraMap (A ⊗[R] S) (Localization.AtPrime q)) x
x s : A ⊗[R] S
hs : s ∈ q.primeCompl
⊢ ∃ s_1, IsUnit (f s_1) ∧ IsLocalization.mk' (Localization.AtPrime q) x ⟨s, hs⟩ * f s_1 ∈ f.range
Module: Mathlib.RingTheory.QuasiFinite.Basic

Goal state before:
pp: R : Type u_1
S : Type u_2
inst✝⁴ : CommRing R
inst✝³ : CommRing S
inst✝² : Algebra R S
inst✝¹ : IsArtinianRing R
p : PrimeSpectrum S
inst✝ : FiniteType R S
H✝ : IsClopen {p}
this✝³ : IsNoetherianRing S
this✝² : IsJacobsonRing S
e : S
he : IsIdempotentElem e
H : {p} = ↑(PrimeSpectrum.basicOpen e)
hep : e ∉ p.asIdeal
f : Localization.Away e →ₐ[S] Localization.AtPrime p.asIdeal := IsLocalization.Away.liftAlgHom e ⋯
h₁ : Set.range (PrimeSpectrum.comap (algebraMap S (Localization.Away e))) = {p}
this✝¹ : Subsingleton (PrimeSpectrum (Localization.Away e))
hf : Function.Surjective ⇑f
this✝ : FiniteType R (Localization.AtPrime p.asIdeal)
this : Subsingleton (PrimeSpectrum (Localization.AtPrime p.asIdeal))
⊢ QuasiFiniteAt R p.asIdeal

Tactic:
exact QuasiFinite.iff_finite_comap_preimage_singleton.mpr fun _ ↦
    Set.subsingleton_of_subsingleton.finite

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

Goal state before:
pp: R : Type u
A : Type v
inst✝⁹ : CommRing R
inst✝⁸ : CommRing A
inst✝⁷ : Algebra R A
B : Type u_1
P : Type u_2
C : Type u_3
inst✝⁶ : CommRing B
inst✝⁵ : Algebra R B
inst✝⁴ : CommRing C
inst✝³ : Algebra R C
inst✝² : CommRing P
inst✝¹ : Algebra R P
P₁ : Extension R A
P₂ : Extension R A
inst✝ : FormallySmooth R P₁.Ring
lift : P₁.Ring →ₐ[R] P₂.infinitesimal.Ring :=
  FormallySmooth.liftOfSurjective (IsScalarTower.toAlgHom R P₁.Ring A)
    (IsScalarTower.toAlgHom R P₂.infinitesimal.Ring A) ⋯ ⋯
⊢ P₁.ker ^ 2 ≤ RingHom.ker lift

Tactic:
pow_two,

Goal state after:
R : Type u
A : Type v
inst✝⁹ : CommRing R
inst✝⁸ : CommRing A
inst✝⁷ : Algebra R A
B : Type u_1
P : Type u_2
C : Type u_3
inst✝⁶ : CommRing B
inst✝⁵ : Algebra R B
inst✝⁴ : CommRing C
inst✝³ : Algebra R C
inst✝² : CommRing P
inst✝¹ : Algebra R P
P₁ : Extension R A
P₂ : Extension R A
inst✝ : FormallySmooth R P₁.Ring
lift : P₁.Ring →ₐ[R] P₂.infinitesimal.Ring :=
  FormallySmooth.liftOfSurjective (IsScalarTower.toAlgHom R P₁.Ring A)
    (IsScalarTower.toAlgHom R P₂.infinitesimal.Ring A) ⋯ ⋯
⊢ P₁.ker * P₁.ker ≤ RingHom.ker lift
Module: Mathlib.RingTheory.Kaehler.JacobiZariski

Goal state before:
pp: case h2
R : Type u₁
S : Type u₂
inst✝⁶ : CommRing R
inst✝⁵ : CommRing S
inst✝⁴ : Algebra R S
T : Type u₃
inst✝³ : CommRing T
inst✝² : Algebra R T
inst✝¹ : Algebra S T
inst✝ : IsScalarTower R S T
ι : Type w₁
σ : Type w₂
Q : Generators S T ι
P : Generators R S σ
x : (Q.comp P).Ring
hx' : x ∈ (Q.comp P).toExtension.ker
hx : (Q.ofComp P).toAlgHom x ∈ Q.ker ^ 2
⊢ Extension.Cotangent.mk ⟨x, hx'⟩ ∈
    (LinearMap.liftBaseChange T (Extension.Cotangent.map (Q.toComp P).toExtensionHom)).range

Tactic:
pow_two,

Goal state after:
case h2
R : Type u₁
S : Type u₂
inst✝⁶ : CommRing R
inst✝⁵ : CommRing S
inst✝⁴ : Algebra R S
T : Type u₃
inst✝³ : CommRing T
inst✝² : Algebra R T
inst✝¹ : Algebra S T
inst✝ : IsScalarTower R S T
ι : Type w₁
σ : Type w₂
Q : Generators S T ι
P : Generators R S σ
x : (Q.comp P).Ring
hx' : x ∈ (Q.comp P).toExtension.ker
hx : (Q.ofComp P).toAlgHom x ∈ Q.ker * Q.ker
⊢ Extension.Cotangent.mk ⟨x, hx'⟩ ∈
    (LinearMap.liftBaseChange T (Extension.Cotangent.map (Q.toComp P).toExtensionHom)).range
Module: Mathlib.RingTheory.Kaehler.JacobiZariski

Goal state before:
pp: case h2
R : Type u₁
S : Type u₂
inst✝⁶ : CommRing R
inst✝⁵ : CommRing S
inst✝⁴ : Algebra R S
T : Type u₃
inst✝³ : CommRing T
inst✝² : Algebra R T
inst✝¹ : Algebra S T
inst✝ : IsScalarTower R S T
ι : Type w₁
σ : Type w₂
Q : Generators S T ι
P : Generators R S σ
x : (Q.comp P).Ring
hx' : x ∈ (Q.comp P).toExtension.ker
y : (Q.comp P).Ring
hy : y ∈ (Q.comp P).ker * (Q.comp P).ker
e : x - y ∈ Ideal.map (Q.toComp P).toAlgHom P.ker
⊢ Extension.Cotangent.mk ⟨x, hx'⟩ ∈
    (LinearMap.liftBaseChange T (Extension.Cotangent.map (Q.toComp P).toExtensionHom)).range

Tactic:
LinearMap.range_liftBaseChange

Goal state after:
case h2
R : Type u₁
S : Type u₂
inst✝⁶ : CommRing R
inst✝⁵ : CommRing S
inst✝⁴ : Algebra R S
T : Type u₃
inst✝³ : CommRing T
inst✝² : Algebra R T
inst✝¹ : Algebra S T
inst✝ : IsScalarTower R S T
ι : Type w₁
σ : Type w₂
Q : Generators S T ι
P : Generators R S σ
x : (Q.comp P).Ring
hx' : x ∈ (Q.comp P).toExtension.ker
y : (Q.comp P).Ring
hy : y ∈ (Q.comp P).ker * (Q.comp P).ker
e : x - y ∈ Ideal.map (Q.toComp P).toAlgHom P.ker
⊢ Extension.Cotangent.mk ⟨x, hx'⟩ ∈ Submodule.span T ↑(Extension.Cotangent.map (Q.toComp P).toExtensionHom).range
Module: Mathlib.RingTheory.Kaehler.JacobiZariski

Goal state before:
pp: R : Type u₁
S : Type u₂
inst✝⁶ : CommRing R
inst✝⁵ : CommRing S
inst✝⁴ : Algebra R S
T : Type u₃
inst✝³ : CommRing T
inst✝² : Algebra R T
inst✝¹ : Algebra S T
inst✝ : IsScalarTower R S T
ι : Type w₁
Q : Generators S T ι
n : ι →₀ ℕ
r : S
⊢ (δAux R Q) ((monomial n) r) = (n.prod fun x1 x2 ↦ Q.val x1 ^ x2) ⊗ₜ[S] (D R S) r

Tactic:
by simp [δAux]

Goal state after:
Module: Mathlib.RingTheory.Smooth.Kaehler

Goal state before:
pp: case e_a
R : Type u_1
P : Type u_2
S : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing P
inst✝⁴ : CommRing S
inst✝³ : Algebra R P
inst✝² : Algebra P S
inst✝¹ : Algebra R S
inst✝ : IsScalarTower R P S
g : S →ₐ[R] P
hf' : RingHom.ker (algebraMap P S) ^ 2 = ⊥
hg : (IsScalarTower.toAlgHom R P S).comp g = AlgHom.id R S
this : Algebra S P := g.toAlgebra
p : P
s : S
m : ↥(RingHom.ker (algebraMap P S))
⊢ g ((algebraMap P S) p) * ↑m - p * ↑m ∈ RingHom.ker (algebraMap P S) ^ 2

Tactic:
pow_two,

Goal state after:
case e_a
R : Type u_1
P : Type u_2
S : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing P
inst✝⁴ : CommRing S
inst✝³ : Algebra R P
inst✝² : Algebra P S
inst✝¹ : Algebra R S
inst✝ : IsScalarTower R P S
g : S →ₐ[R] P
hf' : RingHom.ker (algebraMap P S) ^ 2 = ⊥
hg : (IsScalarTower.toAlgHom R P S).comp g = AlgHom.id R S
this : Algebra S P := g.toAlgebra
p : P
s : S
m : ↥(RingHom.ker (algebraMap P S))
⊢ g ((algebraMap P S) p) * ↑m - p * ↑m ∈ RingHom.ker (algebraMap P S) * RingHom.ker (algebraMap P S)
Module: Mathlib.RingTheory.Smooth.Kaehler

Goal state before:
pp: case refine_3
R : Type u_1
P : Type u_2
S : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing P
inst✝⁴ : CommRing S
inst✝³ : Algebra R P
inst✝² : Algebra P S
inst✝¹ : Algebra R S
inst✝ : IsScalarTower R P S
hf' : RingHom.ker (algebraMap P S) ^ 2 = ⊥
hf : Surjective ⇑(algebraMap P S)
this : Submodule.restrictScalars R (RingHom.ker (algebraMap P S) ^ 2) ≤ (↑R ((mk P S Ω[P⁄R]) 1) ∘ₗ ↑(D R P)).ker →
  P ⧸ Submodule.restrictScalars R (RingHom.ker (algebraMap P S) ^ 2) →ₗ[R] S ⊗[P] Ω[P⁄R] :=
  (Submodule.restrictScalars R (RingHom.ker (algebraMap P S) ^ 2)).liftQ (↑R ((mk P S Ω[P⁄R]) 1) ∘ₗ ↑(D R P))
b : P ⧸ RingHom.ker (algebraMap P S) ^ 2
a : P
⊢ (this ⋯) (Submodule.Quotient.mk a * b) = Submodule.Quotient.mk a • (this ⋯) b + b • (this ⋯) (Submodule.Quotient.mk a)

Tactic:
obtain ⟨b, rfl⟩ := Submodule.Quotient.mk_surjective _ b

Goal state after:
case refine_3
R : Type u_1
P : Type u_2
S : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing P
inst✝⁴ : CommRing S
inst✝³ : Algebra R P
inst✝² : Algebra P S
inst✝¹ : Algebra R S
inst✝ : IsScalarTower R P S
hf' : RingHom.ker (algebraMap P S) ^ 2 = ⊥
hf : Surjective ⇑(algebraMap P S)
this : Submodule.restrictScalars R (RingHom.ker (algebraMap P S) ^ 2) ≤ (↑R ((mk P S Ω[P⁄R]) 1) ∘ₗ ↑(D R P)).ker →
  P ⧸ Submodule.restrictScalars R (RingHom.ker (algebraMap P S) ^ 2) →ₗ[R] S ⊗[P] Ω[P⁄R] :=
  (Submodule.restrictScalars R (RingHom.ker (algebraMap P S) ^ 2)).liftQ (↑R ((mk P S Ω[P⁄R]) 1) ∘ₗ ↑(D R P))
a b : P
⊢ (this ⋯) (Submodule.Quotient.mk a * Submodule.Quotient.mk b) =
    Submodule.Quotient.mk a • (this ⋯) (Submodule.Quotient.mk b) +
      Submodule.Quotient.mk b • (this ⋯) (Submodule.Quotient.mk a)
Module: Mathlib.RingTheory.Unramified.Field

Goal state before:
pp: K : Type u_1
A : Type u_2
inst✝⁶ : Field K
inst✝⁵ : CommRing A
inst✝⁴ : Algebra K A
inst✝³ : FormallyUnramified K A
inst✝² : EssFiniteType K A
inst✝¹ : IsAlgClosed K
inst✝ : IsLocalRing A
⊢ Function.Bijective ⇑(algebraMap K A)

Tactic:
by
  have := finite_of_free (R := K) (S := A)
  have : IsArtinianRing A := isArtinian_of_tower K inferInstance
  have hA : IsNilpotent (IsLocalRing.maximalIdeal A) := by
    rw [← IsLocalRing.jacobson_eq_maximalIdeal ⊥]
    · exact IsArtinianRing.isNilpotent_jacobson_bot
    · exact bot_ne_top
  let e : K ≃ₐ[K] A ⧸ IsLocalRing.maximalIdeal A := {
    __ := Algebra.ofId K (A ⧸ IsLocalRing.maximalIdeal A)
    __ := Equiv.ofBijective _ IsAlgClosed.algebraMap_bijective_of_isIntegral }
  let e' : A ⊗[K] (A ⧸ IsLocalRing.maximalIdeal A) ≃ₐ[A] A :=
    (Algebra.TensorProduct.congr AlgEquiv.refl e.symm).trans (Algebra.TensorProduct.rid K A A)
  let f : A ⧸ IsLocalRing.maximalIdeal A →ₗ[A] A := e'.toLinearMap.comp (sec K A _)
  have hf : (Algebra.ofId _ _).toLinearMap ∘ₗ f = LinearMap.id := by
    dsimp [f]
    rw [← LinearMap.comp_assoc, ← comp_sec K A]
    congr 1
    apply LinearMap.restrictScalars_injective K
    apply _root_.TensorProduct.ext'
    intro r s
    obtain ⟨s, rfl⟩ := e.surjective s
    suffices s • (Ideal.Quotient.mk (IsLocalRing.maximalIdeal A)) r = r • e s by
      simpa [ofId, e']
    simp [Algebra.smul_def, e, ofId, mul_comm]
  have hf₁ : f 1 • (1 : A ⧸ IsLocalRing.maximalIdeal A) = 1 := by
    rw [← algebraMap_eq_smul_one]
    exact LinearMap.congr_fun hf 1
  have hf₂ : 1 - f 1 ∈ IsLocalRing.maximalIdeal A := by
    rw [← Ideal.Quotient.eq_zero_iff_mem, map_sub, map_one, ← Ideal.Quotient.algebraMap_eq,
     algebraMap_eq_smul_one, hf₁, sub_self]
  have hf₃ : IsIdempotentElem (1 - f 1) := by
    apply IsIdempotentElem.one_sub
    rw [IsIdempotentElem, ← smul_eq_mul, ← map_smul, hf₁]
  have hf₄ : f 1 = 1 := by
    obtain ⟨n, hn⟩ := hA
    have : (1 - f 1) ^ n = 0 := by
      rw [← Ideal.mem_bot, ← Ideal.zero_eq_bot, ← hn]
      exact Ideal.pow_mem_pow hf₂ n
    rw [eq_comm, ← sub_eq_zero, ← hf₃.pow_succ_eq n, pow_succ, this, zero_mul]
  refine Equiv.bijective ⟨algebraMap K A, ⇑e.symm ∘ ⇑(algebraMap A _), fun x ↦ by simp, fun x ↦ ?_⟩
  have : ⇑(algebraMap K A) = ⇑f ∘ ⇑e := by
    ext k
    conv_rhs => rw [← mul_one k, ← smul_eq_mul, Function.comp_apply, map_smul,
      LinearMap.map_smul_of_tower, map_one, hf₄, ← algebraMap_eq_smul_one]
  rw [this]
  simp only [Function.comp_apply, AlgEquiv.apply_symm_apply, algebraMap_eq_smul_one,
    map_smul, hf₄, smul_eq_mul, mul_one]

Goal state after:
Module: Mathlib.RingTheory.Unramified.Field

Goal state before:
pp: K : Type u_1
L : Type u_3
inst✝⁵ : Field K
inst✝⁴ : Field L
inst✝³ : Algebra K L
inst✝² : FormallyUnramified K L
inst✝¹ : EssFiniteType K L
inst✝ : IsPurelyInseparable K L
this✝¹ : Nontrivial (L ⊗[K] L)
x : L
a✝ : x ∈ ⊤
n : ℕ
hn : x ^ ringExpChar K ^ n ∈ (algebraMap K L).range
this✝ : ExpChar (L ⊗[K] L) (ringExpChar K)
this : (1 ⊗ₜ[K] x - x ⊗ₜ[K] 1) ^ ringExpChar K ^ n = 0
⊢ x ∈ (algebraMap K L).range

Tactic:
have H : (1 ⊗ₜ x : L ⊗[K] L) = x ⊗ₜ 1 := by
    have inst : IsReduced (L ⊗[K] L) := isReduced_of_field L _
    exact sub_eq_zero.mp (IsNilpotent.eq_zero ⟨_, this⟩)

Goal state after:
K : Type u_1
L : Type u_3
inst✝⁵ : Field K
inst✝⁴ : Field L
inst✝³ : Algebra K L
inst✝² : FormallyUnramified K L
inst✝¹ : EssFiniteType K L
inst✝ : IsPurelyInseparable K L
this✝¹ : Nontrivial (L ⊗[K] L)
x : L
a✝ : x ∈ ⊤
n : ℕ
hn : x ^ ringExpChar K ^ n ∈ (algebraMap K L).range
this✝ : ExpChar (L ⊗[K] L) (ringExpChar K)
this : (1 ⊗ₜ[K] x - x ⊗ₜ[K] 1) ^ ringExpChar K ^ n = 0
H : 1 ⊗ₜ[K] x = x ⊗ₜ[K] 1
⊢ x ∈ (algebraMap K L).range
Module: Mathlib.RingTheory.Smooth.Kaehler

Goal state before:
pp: case refine_3
R : Type u_1
P : Type u_2
S : Type u_3
inst✝⁶ : CommRing R
inst✝⁵ : CommRing P
inst✝⁴ : CommRing S
inst✝³ : Algebra R P
inst✝² : Algebra P S
inst✝¹ : Algebra R S
inst✝ : IsScalarTower R P S
hf' : RingHom.ker (algebraMap P S) ^ 2 = ⊥
hf : Surjective ⇑(algebraMap P S)
P' : Type u_2 := P ⧸ RingHom.ker (algebraMap P S) ^ 2
h₁ : Surjective ⇑(algebraMap P' S)
h₂ : RingHom.ker (algebraMap P' S) ^ 2 = ⊥
e₁ : (RingHom.ker (algebraMap P S)).Cotangent ≃ₗ[P] ↥(RingHom.ker (algebraMap P' S)) :=
  (RingHom.ker (algebraMap P S)).cotangentEquivIdeal ≪≫ₗ
    LinearEquiv.restrictScalars P
      (LinearEquiv.ofEq (RingHom.ker (IsScalarTower.toAlgHom R P S).toRingHom).cotangentIdeal
        (RingHom.ker (IsScalarTower.toAlgHom R P S).kerSquareLift.toRingHom) ⋯)
e₂ : S ⊗[P'] Ω[P'⁄R] ≃ₗ[P] S ⊗[P] Ω[P⁄R] := LinearEquiv.restrictScalars P (tensorKaehlerQuotKerSqEquiv R P S)
H : kerCotangentToTensor R P S = ↑e₂ ∘ₗ ↑P (kerToTensor R P' S) ∘ₗ ↑e₁
x✝ : { l // l ∘ₗ kerToTensor R P' S = LinearMap.id }
l : S ⊗[P'] Ω[P'⁄R] →ₗ[P'] ↥(RingHom.ker (algebraMap P' S))
hl : l ∘ₗ kerToTensor R P' S = LinearMap.id
⊢ (↑e₁.symm ∘ₗ ↑P l ∘ₗ ↑e₂.symm) ∘ₗ kerCotangentToTensor R P S = LinearMap.id

Tactic:
ext x
    rw [H]
    apply e₁.injective
    simp only [LinearMap.coe_comp, LinearEquiv.coe_coe, LinearMap.coe_restrictScalars,
      Function.comp_apply, LinearEquiv.symm_apply_apply, LinearMap.id_coe, id_eq,
      LinearEquiv.apply_symm_apply]
    exact LinearMap.congr_fun hl (e₁ x)

Goal state after:
Module: Mathlib.RingTheory.Kaehler.JacobiZariski

Goal state before:
pp: R : Type u₁
S : Type u₂
inst✝⁶ : CommRing R
inst✝⁵ : CommRing S
inst✝⁴ : Algebra R S
T : Type u₃
inst✝³ : CommRing T
inst✝² : Algebra R T
inst✝¹ : Algebra S T
inst✝ : IsScalarTower R S T
ι : Type w₁
σ : Type w₂
τ : Type w₅
Q : Generators S T ι
P : Generators R S σ
W : Generators R T τ
f : W.Hom Q
⊢ Function.Exact ⇑(Extension.H1Cotangent.map (Q.ofComp P).toExtensionHom) ⇑(δ Q P)

Tactic:
exact exact_map_δ Q P

Goal state after:
Module: Mathlib.RingTheory.Etale.Kaehler

Goal state before:
pp: case right
R : Type u_1
S : Type u_2
T : Type u_3
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
inst✝⁵ : CommRing T
inst✝⁴ : Algebra R S
inst✝³ : Algebra R T
inst✝² : Algebra S T
inst✝¹ : IsScalarTower R S T
P : Extension R S
Q : Extension R T
f : P.Hom Q
alg : Algebra P.Ring Q.Ring
halg : algebraMap P.Ring Q.Ring = f.toRingHom
inst✝ : Module.Flat S T
H₁ : f.toRingHom.FormallyEtale
H₂ : Function.Bijective ⇑(LinearMap.liftBaseChange Q.Ring (f.mapKer halg))
x : Q.H1Cotangent
⊢ ∃ a, (LinearMap.liftBaseChange T (H1Cotangent.map f)) a = x

Tactic:
have : Function.Exact (h1Cotangentι.baseChange T) (P.cotangentComplex.baseChange T) :=
      Module.Flat.lTensor_exact T (LinearMap.exact_subtype_ker_map _)

Goal state after:
case right
R : Type u_1
S : Type u_2
T : Type u_3
inst✝⁷ : CommRing R
inst✝⁶ : CommRing S
inst✝⁵ : CommRing T
inst✝⁴ : Algebra R S
inst✝³ : Algebra R T
inst✝² : Algebra S T
inst✝¹ : IsScalarTower R S T
P : Extension R S
Q : Extension R T
f : P.Hom Q
alg : Algebra P.Ring Q.Ring
halg : algebraMap P.Ring Q.Ring = f.toRingHom
inst✝ : Module.Flat S T
H₁ : f.toRingHom.FormallyEtale
H₂ : Function.Bijective ⇑(LinearMap.liftBaseChange Q.Ring (f.mapKer halg))
x : Q.H1Cotangent
this : Function.Exact ⇑(LinearMap.baseChange T h1Cotangentι) ⇑(LinearMap.baseChange T P.cotangentComplex)
⊢ ∃ a, (LinearMap.liftBaseChange T (H1Cotangent.map f)) a = x