Theorem: Ideal.algebraMap_quotient_injective
File: Mathlib/RingTheory/Ideal/QuotientOperations.lean

tactic: rintro ⟨a⟩ ⟨b⟩ hab
state_before: R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
⊢ Injective ⇑(algebraMap (R ⧸ comap (algebraMap R A) I) (A ⧸ I))
state_after: case mk.mk
R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
a₁✝ : R ⧸ comap (algebraMap R A) I
a : R
a₂✝ : R ⧸ comap (algebraMap R A) I
b : R
hab :
  (algebraMap (R ⧸ comap (algebraMap R A) I) (A ⧸ I)) (Quot.mk Setoid.r a) =
    (algebraMap (R ⧸ comap (algebraMap R A) I) (A ⧸ I)) (Quot.mk Setoid.r b)
⊢ Quot.mk Setoid.r a = Quot.mk Setoid.r b

tactic: replace hab := Quotient.eq.mp hab
state_before: case mk.mk
R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
a₁✝ : R ⧸ comap (algebraMap R A) I
a : R
a₂✝ : R ⧸ comap (algebraMap R A) I
b : R
hab :
  (algebraMap (R ⧸ comap (algebraMap R A) I) (A ⧸ I)) (Quot.mk Setoid.r a) =
    (algebraMap (R ⧸ comap (algebraMap R A) I) (A ⧸ I)) (Quot.mk Setoid.r b)
⊢ Quot.mk Setoid.r a = Quot.mk Setoid.r b
state_after: case mk.mk
R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
a₁✝ : R ⧸ comap (algebraMap R A) I
a : R
a₂✝ : R ⧸ comap (algebraMap R A) I
b : R
hab : (algebraMap R A) a - (algebraMap R A) b ∈ I
⊢ Quot.mk Setoid.r a = Quot.mk Setoid.r b

tactic: rw [← RingHom.map_sub] at hab
state_before: case mk.mk
R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
a₁✝ : R ⧸ comap (algebraMap R A) I
a : R
a₂✝ : R ⧸ comap (algebraMap R A) I
b : R
hab : (algebraMap R A) a - (algebraMap R A) b ∈ I
⊢ Quot.mk Setoid.r a = Quot.mk Setoid.r b
state_after: case mk.mk
R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
a₁✝ : R ⧸ comap (algebraMap R A) I
a : R
a₂✝ : R ⧸ comap (algebraMap R A) I
b : R
hab : (algebraMap R A) (a - b) ∈ I
⊢ Quot.mk Setoid.r a = Quot.mk Setoid.r b

tactic: exact Quotient.eq.mpr hab
state_before: case mk.mk
R : Type u
S : Type v
F : Type w
inst✝⁷ : CommRing R
inst✝⁶ : Semiring S
R₁ : Type u_1
R₂ : Type u_2
A : Type u_3
B : Type u_4
inst✝⁵ : CommSemiring R₁
inst✝⁴ : CommSemiring R₂
inst✝³ : CommRing A
inst✝² : Algebra R₁ A
inst✝¹ : Algebra R₂ A
I : Ideal A
inst✝ : Algebra R A
a₁✝ : R ⧸ comap (algebraMap R A) I
a : R
a₂✝ : R ⧸ comap (algebraMap R A) I
b : R
hab : (algebraMap R A) (a - b) ∈ I
⊢ Quot.mk Setoid.r a = Quot.mk Setoid.r b
state_after: no goals