-- Mathlib/RingTheory/Localization/Integral.lean
theorem isIntegral_localization [Algebra.IsIntegral R S] :
    (map Sₘ (algebraMap R S)
          (show _ ≤ (Algebra.algebraMapSubmonoid S M).comap _ from M.le_comap_map) :
        Rₘ →+* _).IsIntegral

Proof state:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : v' * (algebraMap R Rₘ) ↑⟨v, ⋯⟩ = 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1

Tactic:
replace hv' := congr_arg (@algebraMap Rₘ Sₘ _ _ (localizationAlgebra M S)) hv'

Result:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : (algebraMap Rₘ Sₘ) (v' * (algebraMap R Rₘ) ↑⟨v, ⋯⟩) = (algebraMap Rₘ Sₘ) 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1

Proof state:
case intro.mk.mk
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
hu : u ∈ Algebra.algebraMapSubmonoid S M
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, hu⟩).2 = (algebraMap S Sₘ) (s, ⟨u, hu⟩).1
⊢ (IsLocalization.map Sₘ (algebraMap R S) ⋯).IsIntegralElem x

Tactic:
obtain ⟨v, hv⟩ := hu

Result:
case intro.mk.mk.intro
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
⊢ (IsLocalization.map Sₘ (algebraMap R S) ⋯).IsIntegralElem x

Proof state:
case intro.mk.mk.intro.intro
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : v' * (algebraMap R Rₘ) ↑⟨v, ⋯⟩ = 1
⊢ (IsLocalization.map Sₘ (algebraMap R S) ⋯).IsIntegralElem x

Tactic:
refine @IsIntegral.of_mul_unit Rₘ _ _ _ (localizationAlgebra M S) x (algebraMap S Sₘ u) v' ?_ ?_

Result:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : v' * (algebraMap R Rₘ) ↑⟨v, ⋯⟩ = 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1

case intro.mk.mk.intro.intro.refine_2
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : v' * (algebraMap R Rₘ) ↑⟨v, ⋯⟩ = 1
⊢ IsIntegral Rₘ (x * (algebraMap S Sₘ) u)

Proof state:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : (algebraMap Rₘ Sₘ) (v' * (algebraMap R Rₘ) ↑⟨v, ⋯⟩) = (algebraMap Rₘ Sₘ) 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1

Tactic:
rw [RingHom.map_mul, RingHom.map_one, ← RingHom.comp_apply _ (algebraMap R Rₘ)] at hv'

Result:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : (algebraMap Rₘ Sₘ) v' * ((algebraMap Rₘ Sₘ).comp (algebraMap R Rₘ)) ↑⟨v, ⋯⟩ = 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1

Proof state:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : (algebraMap Rₘ Sₘ) v' * ((algebraMap Rₘ Sₘ).comp (algebraMap R Rₘ)) ↑⟨v, ⋯⟩ = 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1

Tactic:
erw [IsLocalization.map_comp
  (show _ ≤ (Algebra.algebraMapSubmonoid S M).comap _ from M.le_comap_map)] at hv'

Result:
case intro.mk.mk.intro.intro.refine_1
R : Type u_1
inst✝⁹ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁸ : CommRing S
inst✝⁷ : Algebra R S
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁶ : CommRing Rₘ
inst✝⁵ : CommRing Sₘ
inst✝⁴ : Algebra R Rₘ
inst✝³ : IsLocalization M Rₘ
inst✝² : Algebra S Sₘ
inst✝¹ : IsLocalization (Algebra.algebraMapSubmonoid S M) Sₘ
inst✝ : Algebra.IsIntegral R S
x : Sₘ
s u : S
v : R
hv : v ∈ ↑M ∧ (algebraMap R S) v = u
hx : x * (algebraMap S Sₘ) ↑(s, ⟨u, ⋯⟩).2 = (algebraMap S Sₘ) (s, ⟨u, ⋯⟩).1
v' : Rₘ
hv' : (algebraMap Rₘ Sₘ) v' * ((algebraMap S Sₘ).comp (algebraMap R S)) ↑⟨v, ⋯⟩ = 1
⊢ (algebraMap Rₘ Sₘ) v' * (algebraMap S Sₘ) u = 1