Theorem: HenselianLocalRing.TFAE
File: Mathlib/RingTheory/Henselian.lean

tactic: tfae_have 3 → 2
state_before: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE
state_after: case tfae_3_to_2
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
⊢ (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀

R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE

tactic: tfae_have 2 → 1
state_before: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE
state_after: case tfae_2_to_1
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R

R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE

tactic: tfae_have 1 → 3
state_before: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE
state_after: case tfae_1_to_3
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
⊢ HenselianLocalRing R →
    ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀

R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
tfae_1_to_3 :
  HenselianLocalRing R →
    ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE

tactic: tfae_finish
state_before: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
tfae_1_to_3 :
  HenselianLocalRing R →
    ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀
⊢ [HenselianLocalRing R,
      ∀ (f : R[X]),
        f.Monic →
          ∀ (a₀ : ResidueField R),
            (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀,
      ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
        Surjective ⇑φ →
          ∀ (f : R[X]),
            f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀].TFAE
state_after: no goals

tactic: intro H
state_before: case tfae_3_to_2
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
⊢ (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
state_after: case tfae_3_to_2
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
H :
  ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
    Surjective ⇑φ →
      ∀ (f : R[X]), f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀
⊢ ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀

tactic: exact H (residue R) Ideal.Quotient.mk_surjective
state_before: case tfae_3_to_2
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
H :
  ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
    Surjective ⇑φ →
      ∀ (f : R[X]), f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀
⊢ ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
state_after: no goals

tactic: intro H
state_before: case tfae_2_to_1
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
state_after: case tfae_2_to_1
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
H :
  ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ HenselianLocalRing R

tactic: constructor
state_before: case tfae_2_to_1
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
H :
  ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ HenselianLocalRing R
state_after: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
H :
  ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : R),
        Polynomial.eval a₀ f ∈ maximalIdeal R →
          IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R

tactic: intro f hf a₀ h₁ h₂
state_before: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
H :
  ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
⊢ ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : R),
        Polynomial.eval a₀ f ∈ maximalIdeal R →
          IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
H :
  ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₁ : Polynomial.eval a₀ f ∈ maximalIdeal R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R

tactic: specialize H f hf (residue R a₀)
state_before: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
H :
  ∀ (f : R[X]),
    f.Monic →
      ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₁ : Polynomial.eval a₀ f ∈ maximalIdeal R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₁ : Polynomial.eval a₀ f ∈ maximalIdeal R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (aeval ((residue R) a₀)) f = 0 →
    (aeval ((residue R) a₀)) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R

tactic: have aux := flip mem_nonunits_iff.mp h₂
state_before: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₁ : Polynomial.eval a₀ f ∈ maximalIdeal R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (aeval ((residue R) a₀)) f = 0 →
    (aeval ((residue R) a₀)) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₁ : Polynomial.eval a₀ f ∈ maximalIdeal R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (aeval ((residue R) a₀)) f = 0 →
    (aeval ((residue R) a₀)) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
aux : Polynomial.eval a₀ (derivative f) ∈ nonunits R → False
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R

tactic: simp only [aeval_def, ResidueField.algebraMap_eq, eval₂_at_apply, ←
  Ideal.Quotient.eq_zero_iff_mem, ← LocalRing.mem_maximalIdeal] at H h₁ aux
state_before: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₁ : Polynomial.eval a₀ f ∈ maximalIdeal R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (aeval ((residue R) a₀)) f = 0 →
    (aeval ((residue R) a₀)) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
aux : Polynomial.eval a₀ (derivative f) ∈ nonunits R → False
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R

tactic: obtain ⟨a, ha₁, ha₂⟩ := H h₁ aux
state_before: case tfae_2_to_1.is_henselian
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
a : R
ha₁ : f.IsRoot a
ha₂ : (residue R) a = (residue R) a₀
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R

tactic: refine ⟨a, ha₁, ?_⟩
state_before: case tfae_2_to_1.is_henselian.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
a : R
ha₁ : f.IsRoot a
ha₂ : (residue R) a = (residue R) a₀
⊢ ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
a : R
ha₁ : f.IsRoot a
ha₂ : (residue R) a = (residue R) a₀
⊢ a - a₀ ∈ maximalIdeal R

tactic: rw [← Ideal.Quotient.eq_zero_iff_mem]
state_before: case tfae_2_to_1.is_henselian.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
a : R
ha₁ : f.IsRoot a
ha₂ : (residue R) a = (residue R) a₀
⊢ a - a₀ ∈ maximalIdeal R
state_after: case tfae_2_to_1.is_henselian.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
a : R
ha₁ : f.IsRoot a
ha₂ : (residue R) a = (residue R) a₀
⊢ (Ideal.Quotient.mk (maximalIdeal R)) (a - a₀) = 0

tactic: rwa [← sub_eq_zero, ← RingHom.map_sub] at ha₂
state_before: case tfae_2_to_1.is_henselian.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
f : R[X]
hf : f.Monic
a₀ : R
h₂ : IsUnit (Polynomial.eval a₀ (derivative f))
H :
  (residue R) (Polynomial.eval a₀ f) = 0 →
    (residue R) (Polynomial.eval a₀ (derivative f)) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = (residue R) a₀
h₁ : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ f) = 0
aux : (Ideal.Quotient.mk (maximalIdeal R)) (Polynomial.eval a₀ (derivative f)) = 0 → False
a : R
ha₁ : f.IsRoot a
ha₂ : (residue R) a = (residue R) a₀
⊢ (Ideal.Quotient.mk (maximalIdeal R)) (a - a₀) = 0
state_after: no goals

tactic: intro hR K _K φ hφ f hf a₀ h₁ h₂
state_before: case tfae_1_to_3
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
⊢ HenselianLocalRing R →
    ∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀
state_after: case tfae_1_to_3
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : K
h₁ : eval₂ φ a₀ f = 0
h₂ : eval₂ φ a₀ (derivative f) ≠ 0
⊢ ∃ a, f.IsRoot a ∧ φ a = a₀

tactic: obtain ⟨a₀, rfl⟩ := hφ a₀
state_before: case tfae_1_to_3
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : K
h₁ : eval₂ φ a₀ f = 0
h₂ : eval₂ φ a₀ (derivative f) ≠ 0
⊢ ∃ a, f.IsRoot a ∧ φ a = a₀
state_after: case tfae_1_to_3.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
h₁ : eval₂ φ (φ a₀) f = 0
h₂ : eval₂ φ (φ a₀) (derivative f) ≠ 0
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀

tactic: have H := HenselianLocalRing.is_henselian f hf a₀
state_before: case tfae_1_to_3.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
h₁ : eval₂ φ (φ a₀) f = 0
h₂ : eval₂ φ (φ a₀) (derivative f) ≠ 0
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀
state_after: case tfae_1_to_3.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
h₁ : eval₂ φ (φ a₀) f = 0
h₂ : eval₂ φ (φ a₀) (derivative f) ≠ 0
H :
  Polynomial.eval a₀ f ∈ maximalIdeal R →
    IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀

tactic: simp only [← ker_eq_maximalIdeal φ hφ, eval₂_at_apply, RingHom.mem_ker φ] at H h₁ h₂
state_before: case tfae_1_to_3.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
h₁ : eval₂ φ (φ a₀) f = 0
h₂ : eval₂ φ (φ a₀) (derivative f) ≠ 0
H :
  Polynomial.eval a₀ f ∈ maximalIdeal R →
    IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ a - a₀ ∈ maximalIdeal R
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀
state_after: case tfae_1_to_3.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀

tactic: obtain ⟨a, ha₁, ha₂⟩ := H h₁ (by
  contrapose! h₂
  rwa [← mem_nonunits_iff, ← LocalRing.mem_maximalIdeal, ← LocalRing.ker_eq_maximalIdeal φ hφ,
    RingHom.mem_ker] at h₂)
state_before: case tfae_1_to_3.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀
state_after: case tfae_1_to_3.intro.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
a : R
ha₁ : f.IsRoot a
ha₂ : φ (a - a₀) = 0
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀

tactic: refine ⟨a, ha₁, ?_⟩
state_before: case tfae_1_to_3.intro.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
a : R
ha₁ : f.IsRoot a
ha₂ : φ (a - a₀) = 0
⊢ ∃ a, f.IsRoot a ∧ φ a = φ a₀
state_after: case tfae_1_to_3.intro.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
a : R
ha₁ : f.IsRoot a
ha₂ : φ (a - a₀) = 0
⊢ φ a = φ a₀

tactic: rwa [φ.map_sub, sub_eq_zero] at ha₂
state_before: case tfae_1_to_3.intro.intro.intro
R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
a : R
ha₁ : f.IsRoot a
ha₂ : φ (a - a₀) = 0
⊢ φ a = φ a₀
state_after: no goals

tactic: contrapose! h₂
state_before: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : φ (Polynomial.eval a₀ (derivative f)) ≠ 0
⊢ IsUnit (Polynomial.eval a₀ (derivative f))
state_after: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : ¬IsUnit (Polynomial.eval a₀ (derivative f))
⊢ φ (Polynomial.eval a₀ (derivative f)) = 0

tactic: rwa [← mem_nonunits_iff, ← LocalRing.mem_maximalIdeal, ← LocalRing.ker_eq_maximalIdeal φ hφ,
  RingHom.mem_ker] at h₂
state_before: R : Type u
inst✝¹ : CommRing R
inst✝ : LocalRing R
tfae_3_to_2 :
  (∀ {K : Type u} [inst : Field K] (φ : R →+* K),
      Surjective ⇑φ →
        ∀ (f : R[X]),
          f.Monic → ∀ (a₀ : K), eval₂ φ a₀ f = 0 → eval₂ φ a₀ (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ φ a = a₀) →
    ∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R), (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀
tfae_2_to_1 :
  (∀ (f : R[X]),
      f.Monic →
        ∀ (a₀ : ResidueField R),
          (aeval a₀) f = 0 → (aeval a₀) (derivative f) ≠ 0 → ∃ a, f.IsRoot a ∧ (residue R) a = a₀) →
    HenselianLocalRing R
hR : HenselianLocalRing R
K : Type u
_K : Field K
φ : R →+* K
hφ : Surjective ⇑φ
f : R[X]
hf : f.Monic
a₀ : R
H : φ (Polynomial.eval a₀ f) = 0 → IsUnit (Polynomial.eval a₀ (derivative f)) → ∃ a, f.IsRoot a ∧ φ (a - a₀) = 0
h₁ : φ (Polynomial.eval a₀ f) = 0
h₂ : ¬IsUnit (Polynomial.eval a₀ (derivative f))
⊢ φ (Polynomial.eval a₀ (derivative f)) = 0
state_after: no goals