Theorem: integralClosure.mem_lifts_of_monic_of_dvd_map
File: Mathlib/RingTheory/Polynomial/GaussLemma.lean

tactic: have := mem_lift_of_splits_of_roots_mem_range (integralClosure R g.SplittingField)
  ((splits_id_iff_splits _).2 <| SplittingField.splits g) (hg.map _) fun a ha =>
    (SetLike.ext_iff.mp (integralClosure R g.SplittingField).range_algebraMap _).mpr <|
      roots_mem_integralClosure hf ?_
state_before: R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
⊢ g ∈ lifts (algebraMap (↥(integralClosure R K)) K)
state_after: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this :
  map (algebraMap K g.SplittingField) g ∈ lifts (algebraMap (↥(integralClosure R g.SplittingField)) g.SplittingField)
⊢ g ∈ lifts (algebraMap (↥(integralClosure R K)) K)

case refine_1
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
a : g.SplittingField
ha : a ∈ (map (algebraMap K g.SplittingField) g).roots
⊢ a ∈ f.aroots g.SplittingField

tactic: rw [aroots_def, IsScalarTower.algebraMap_eq R K _, ← map_map]
state_before: case refine_1
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
a : g.SplittingField
ha : a ∈ (map (algebraMap K g.SplittingField) g).roots
⊢ a ∈ f.aroots g.SplittingField
state_after: case refine_1
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
a : g.SplittingField
ha : a ∈ (map (algebraMap K g.SplittingField) g).roots
⊢ a ∈ (map (algebraMap K g.SplittingField) (map (algebraMap R K) f)).roots

tactic: refine Multiset.mem_of_le (roots.le_of_dvd ((hf.map _).map _).ne_zero ?_) ha
state_before: case refine_1
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
a : g.SplittingField
ha : a ∈ (map (algebraMap K g.SplittingField) g).roots
⊢ a ∈ (map (algebraMap K g.SplittingField) (map (algebraMap R K) f)).roots
state_after: case refine_1
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
a : g.SplittingField
ha : a ∈ (map (algebraMap K g.SplittingField) g).roots
⊢ map (algebraMap K g.SplittingField) g ∣ map (algebraMap K g.SplittingField) (map (algebraMap R K) f)

tactic: exact map_dvd (algebraMap K g.SplittingField) hd
state_before: case refine_1
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
a : g.SplittingField
ha : a ∈ (map (algebraMap K g.SplittingField) g).roots
⊢ map (algebraMap K g.SplittingField) g ∣ map (algebraMap K g.SplittingField) (map (algebraMap R K) f)
state_after: no goals

tactic: rw [lifts_iff_coeff_lifts, ← RingHom.coe_range, Subalgebra.range_algebraMap] at this
state_before: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this :
  map (algebraMap K g.SplittingField) g ∈ lifts (algebraMap (↥(integralClosure R g.SplittingField)) g.SplittingField)
⊢ g ∈ lifts (algebraMap (↥(integralClosure R K)) K)
state_after: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
⊢ g ∈ lifts (algebraMap (↥(integralClosure R K)) K)

tactic: refine (lifts_iff_coeff_lifts _).2 fun n => ?_
state_before: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
⊢ g ∈ lifts (algebraMap (↥(integralClosure R K)) K)
state_after: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
⊢ g.coeff n ∈ Set.range ⇑(algebraMap (↥(integralClosure R K)) K)

tactic: rw [← RingHom.coe_range, Subalgebra.range_algebraMap]
state_before: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
⊢ g.coeff n ∈ Set.range ⇑(algebraMap (↥(integralClosure R K)) K)
state_after: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
⊢ g.coeff n ∈ ↑(integralClosure R K).toSubring

tactic: obtain ⟨p, hp, he⟩ := SetLike.mem_coe.mp (this n)
state_before: case refine_2
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
⊢ g.coeff n ∈ ↑(integralClosure R K).toSubring
state_after: case refine_2.intro.intro
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : eval₂ (algebraMap R g.SplittingField) ((map (algebraMap K g.SplittingField) g).coeff n) p = 0
⊢ g.coeff n ∈ ↑(integralClosure R K).toSubring

tactic: use p, hp
state_before: case refine_2.intro.intro
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : eval₂ (algebraMap R g.SplittingField) ((map (algebraMap K g.SplittingField) g).coeff n) p = 0
⊢ g.coeff n ∈ ↑(integralClosure R K).toSubring
state_after: case right
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : eval₂ (algebraMap R g.SplittingField) ((map (algebraMap K g.SplittingField) g).coeff n) p = 0
⊢ eval₂ (algebraMap R K) (g.coeff n) p = 0

tactic: rw [IsScalarTower.algebraMap_eq R K, coeff_map, ← eval₂_map, eval₂_at_apply] at he
state_before: case right
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : eval₂ (algebraMap R g.SplittingField) ((map (algebraMap K g.SplittingField) g).coeff n) p = 0
⊢ eval₂ (algebraMap R K) (g.coeff n) p = 0
state_after: case right
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : (algebraMap K g.SplittingField) (eval (g.coeff n) (map (algebraMap R K) p)) = 0
⊢ eval₂ (algebraMap R K) (g.coeff n) p = 0

tactic: rw [eval₂_eq_eval_map]
state_before: case right
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : (algebraMap K g.SplittingField) (eval (g.coeff n) (map (algebraMap R K) p)) = 0
⊢ eval₂ (algebraMap R K) (g.coeff n) p = 0
state_after: case right
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : (algebraMap K g.SplittingField) (eval (g.coeff n) (map (algebraMap R K) p)) = 0
⊢ eval (g.coeff n) (map (algebraMap R K) p) = 0

tactic: apply (injective_iff_map_eq_zero _).1 _ _ he
state_before: case right
R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : (algebraMap K g.SplittingField) (eval (g.coeff n) (map (algebraMap R K) p)) = 0
⊢ eval (g.coeff n) (map (algebraMap R K) p) = 0
state_after: R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : (algebraMap K g.SplittingField) (eval (g.coeff n) (map (algebraMap R K) p)) = 0
⊢ Function.Injective ⇑(algebraMap K g.SplittingField)

tactic: apply RingHom.injective
state_before: R : Type u_1
inst✝² : CommRing R
K : Type u_2
inst✝¹ : Field K
inst✝ : Algebra R K
f : R[X]
hf : f.Monic
g : K[X]
hg : g.Monic
hd : g ∣ map (algebraMap R K) f
this : ∀ (n : ℕ), (map (algebraMap K g.SplittingField) g).coeff n ∈ ↑(integralClosure R g.SplittingField).toSubring
n : ℕ
p : R[X]
hp : p.Monic
he : (algebraMap K g.SplittingField) (eval (g.coeff n) (map (algebraMap R K) p)) = 0
⊢ Function.Injective ⇑(algebraMap K g.SplittingField)
state_after: no goals