Theorem: Polynomial.isUnit_or_eq_zero_of_isUnit_integerNormalization_primPart
File: Mathlib/RingTheory/Polynomial/GaussLemma.lean

Proof steps:
state_before: R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
⊢ IsUnit p
state_after: case intro.intro.intro
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
⊢ IsUnit p
tactic: rcases isUnit_iff.1 h with ⟨_, ⟨u, rfl⟩, hu⟩
state_before: case intro.intro.intro
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
⊢ IsUnit p
state_after: case intro.intro.intro.intro.mk
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = ↑⟨c, c0⟩ • p
⊢ IsUnit p
tactic: obtain ⟨⟨c, c0⟩, hc⟩ := integerNormalization_map_to_map R⁰ p
state_before: case intro.intro.intro.intro.mk
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = ↑⟨c, c0⟩ • p
⊢ IsUnit p
state_after: case intro.intro.intro.intro.mk
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ IsUnit p
tactic: rw [Subtype.coe_mk, Algebra.smul_def, algebraMap_apply] at hc
state_before: case intro.intro.intro.intro.mk
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ IsUnit p
state_after: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ IsUnit (?intro.intro.intro.intro.mk.x * p)

case intro.intro.intro.intro.mk.x
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ K[X]
tactic: apply isUnit_of_mul_isUnit_right
state_before: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ IsUnit (?intro.intro.intro.intro.mk.x * p)

case intro.intro.intro.intro.mk.x
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ K[X]
state_after: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ ∃ r, IsUnit r ∧ C r = map (algebraMap R K) (C ((integerNormalization R⁰ p).content * ↑u))
tactic: rw [← hc, (integerNormalization R⁰ p).eq_C_content_mul_primPart, ← hu, ← RingHom.map_mul,
    isUnit_iff]
state_before: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
⊢ ∃ r, IsUnit r ∧ C r = map (algebraMap R K) (C ((integerNormalization R⁰ p).content * ↑u))
state_after: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : (algebraMap R K) ((integerNormalization R⁰ p).content * ↑u) = 0
⊢ False
tactic: refine
    ⟨algebraMap R K ((integerNormalization R⁰ p).content * ↑u), isUnit_iff_ne_zero.2 fun con => ?_,
      by simp⟩
state_before: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : (algebraMap R K) ((integerNormalization R⁰ p).content * ↑u) = 0
⊢ False
state_after: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : (integerNormalization R⁰ p).content * ↑u = 0
⊢ False
tactic: replace con := (injective_iff_map_eq_zero (algebraMap R K)).1 (IsFractionRing.injective _ _) _ con
state_before: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : (integerNormalization R⁰ p).content * ↑u = 0
⊢ False
state_after: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : p = 0 ∨ ↑u = 0
⊢ False
tactic: rw [mul_eq_zero, content_eq_zero_iff, IsFractionRing.integerNormalization_eq_zero_iff] at con
state_before: case intro.intro.intro.intro.mk.hu
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : p = 0 ∨ ↑u = 0
⊢ False
state_after: case intro.intro.intro.intro.mk.hu.inl
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : p = 0
⊢ False

case intro.intro.intro.intro.mk.hu.inr
R : Type u_1
inst✝⁵ : CommRing R
K : Type u_2
inst✝⁴ : Field K
inst✝³ : Algebra R K
inst✝² : IsFractionRing R K
inst✝¹ : IsDomain R
inst✝ : NormalizedGCDMonoid R
p : K[X]
h0 : p ≠ 0
h : IsUnit (integerNormalization R⁰ p).primPart
u : Rˣ
hu : C ↑u = (integerNormalization R⁰ p).primPart
c : R
c0 : c ∈ R⁰
hc : map (algebraMap R K) (integerNormalization R⁰ p) = C ((algebraMap R K) c) * p
con : ↑u = 0
⊢ False
tactic: rcases con with (con | con)