Theorem: Algebra.discr_eq_discr_of_toMatrix_coeff_isIntegral
File: Mathlib/NumberTheory/NumberField/Discriminant.lean

tactic: replace h' : ∀ i j, IsIntegral ℤ (b'.toMatrix (b.reindex (b.indexEquiv b')) i j) := by
  intro i j
  convert h' i ((b.indexEquiv b').symm j)
  simp [Basis.toMatrix_apply]
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i : ι') (j : ι), IsIntegral ℤ (b'.toMatrix (⇑b) i j)
⊢ discr ℚ ⇑b = discr ℚ ⇑b'
state_after: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
⊢ discr ℚ ⇑b = discr ℚ ⇑b'

tactic: intro i j
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i : ι') (j : ι), IsIntegral ℤ (b'.toMatrix (⇑b) i j)
⊢ ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
state_after: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i : ι') (j : ι), IsIntegral ℤ (b'.toMatrix (⇑b) i j)
i j : ι'
⊢ IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)

tactic: convert h' i ((b.indexEquiv b').symm j)
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i : ι') (j : ι), IsIntegral ℤ (b'.toMatrix (⇑b) i j)
i j : ι'
⊢ IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
state_after: case h.e'_6
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i : ι') (j : ι), IsIntegral ℤ (b'.toMatrix (⇑b) i j)
i j : ι'
⊢ b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j = b'.toMatrix (⇑b) i ((b.indexEquiv b').symm j)

tactic: simp [Basis.toMatrix_apply]
state_before: case h.e'_6
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i : ι') (j : ι), IsIntegral ℤ (b'.toMatrix (⇑b) i j)
i j : ι'
⊢ b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j = b'.toMatrix (⇑b) i ((b.indexEquiv b').symm j)
state_after: no goals

tactic: rw [← (b.reindex (b.indexEquiv b')).toMatrix_map_vecMul b', discr_of_matrix_vecMul,
  ← one_mul (discr ℚ b), Basis.coe_reindex, discr_reindex]
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
⊢ discr ℚ ⇑b = discr ℚ ⇑b'
state_after: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
⊢ 1 * discr ℚ ⇑b = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2 * discr ℚ ⇑b

tactic: congr
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
⊢ 1 * discr ℚ ⇑b = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2 * discr ℚ ⇑b
state_after: case e_a
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2

tactic: have hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix b').det :=
  IsIntegral.det fun i j => h _ _
state_before: case e_a
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2
state_after: case e_a
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2

tactic: obtain ⟨r, hr⟩ := IsIntegrallyClosed.isIntegral_iff.1 hint
state_before: case e_a
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2
state_after: case e_a.intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2

tactic: have hunit : IsUnit r := by
  have : IsIntegral ℤ (b'.toMatrix (b.reindex (b.indexEquiv b'))).det :=
    IsIntegral.det fun i j => h' _ _
  obtain ⟨r', hr'⟩ := IsIntegrallyClosed.isIntegral_iff.1 this
  refine isUnit_iff_exists_inv.2 ⟨r', ?_⟩
  suffices algebraMap ℤ ℚ (r * r') = 1 by
    rw [← RingHom.map_one (algebraMap ℤ ℚ)] at this
    exact (IsFractionRing.injective ℤ ℚ) this
  rw [RingHom.map_mul, hr, hr', ← Matrix.det_mul,
    Basis.toMatrix_mul_toMatrix_flip, Matrix.det_one]
state_before: case e_a.intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2
state_after: case e_a.intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2

tactic: rw [← RingHom.map_one (algebraMap ℤ ℚ), ← hr]
state_before: case e_a.intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
⊢ 1 = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det ^ 2
state_after: case e_a.intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
⊢ (algebraMap ℤ ℚ) 1 = (algebraMap ℤ ℚ) r ^ 2

tactic: cases' Int.isUnit_iff.1 hunit with hp hm
state_before: case e_a.intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
⊢ (algebraMap ℤ ℚ) 1 = (algebraMap ℤ ℚ) r ^ 2
state_after: case e_a.intro.inl
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
hp : r = 1
⊢ (algebraMap ℤ ℚ) 1 = (algebraMap ℤ ℚ) r ^ 2

case e_a.intro.inr
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
hm : r = -1
⊢ (algebraMap ℤ ℚ) 1 = (algebraMap ℤ ℚ) r ^ 2

tactic: have : IsIntegral ℤ (b'.toMatrix (b.reindex (b.indexEquiv b'))).det :=
  IsIntegral.det fun i j => h' _ _
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
⊢ IsUnit r
state_after: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ IsUnit r

tactic: obtain ⟨r', hr'⟩ := IsIntegrallyClosed.isIntegral_iff.1 this
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ IsUnit r
state_after: case intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ IsUnit r

tactic: refine isUnit_iff_exists_inv.2 ⟨r', ?_⟩
state_before: case intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ IsUnit r
state_after: case intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ r * r' = 1

tactic: suffices algebraMap ℤ ℚ (r * r') = 1 by
  rw [← RingHom.map_one (algebraMap ℤ ℚ)] at this
  exact (IsFractionRing.injective ℤ ℚ) this
state_before: case intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ r * r' = 1
state_after: case intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ (algebraMap ℤ ℚ) (r * r') = 1

tactic: rw [RingHom.map_mul, hr, hr', ← Matrix.det_mul,
  Basis.toMatrix_mul_toMatrix_flip, Matrix.det_one]
state_before: case intro
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
⊢ (algebraMap ℤ ℚ) (r * r') = 1
state_after: no goals

tactic: rw [← RingHom.map_one (algebraMap ℤ ℚ)] at this
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this✝ : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
this : (algebraMap ℤ ℚ) (r * r') = 1
⊢ r * r' = 1
state_after: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this✝ : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
this : (algebraMap ℤ ℚ) (r * r') = (algebraMap ℤ ℚ) 1
⊢ r * r' = 1

tactic: exact (IsFractionRing.injective ℤ ℚ) this
state_before: ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
this✝ : IsIntegral ℤ (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
r' : ℤ
hr' : (algebraMap ℤ ℚ) r' = (b'.toMatrix ⇑(b.reindex (b.indexEquiv b'))).det
this : (algebraMap ℤ ℚ) (r * r') = (algebraMap ℤ ℚ) 1
⊢ r * r' = 1
state_after: no goals

tactic: simp [hp]
state_before: case e_a.intro.inl
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
hp : r = 1
⊢ (algebraMap ℤ ℚ) 1 = (algebraMap ℤ ℚ) r ^ 2
state_after: no goals

tactic: simp [hm]
state_before: case e_a.intro.inr
ι : Type u_2
ι' : Type u_3
K : Type u_1
inst✝⁵ : Field K
inst✝⁴ : DecidableEq ι
inst✝³ : DecidableEq ι'
inst✝² : Fintype ι
inst✝¹ : Fintype ι'
inst✝ : NumberField K
b : Basis ι ℚ K
b' : Basis ι' ℚ K
h : ∀ (i : ι) (j : ι'), IsIntegral ℤ (b.toMatrix (⇑b') i j)
h' : ∀ (i j : ι'), IsIntegral ℤ (b'.toMatrix (⇑(b.reindex (b.indexEquiv b'))) i j)
hint : IsIntegral ℤ ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
r : ℤ
hr : (algebraMap ℤ ℚ) r = ((b.reindex (b.indexEquiv b')).toMatrix ⇑b').det
hunit : IsUnit r
hm : r = -1
⊢ (algebraMap ℤ ℚ) 1 = (algebraMap ℤ ℚ) r ^ 2
state_after: no goals