-- Mathlib/Algebra/Algebra/Unitization.lean
/-- If `φ : A →⋆ₙₐ[R] B` is injective, the lift `starMap φ : Unitization R A →⋆ₐ[R] Unitization R B`
is also injective. -/
lemma starMap_injective {φ : A →⋆ₙₐ[R] B} (hφ : Function.Injective φ) :
    Function.Injective (starMap φ)

Proof state:
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ x = y

Tactic:
ext

Result:
case h1
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ x.fst = y.fst

case h2
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ x.snd = y.snd

Proof state:
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ φ x.snd = φ y.snd

Tactic:
simpa [algebraMap_eq_inl] using congr(snd $(h))

Result:
no goals

Proof state:
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
⊢ Function.Injective ⇑(starMap φ)

Tactic:
intro x y h

Result:
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ x = y

Proof state:
case h1
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ x.fst = y.fst

Tactic:
simpa using congr(fst $(h))

Result:
no goals

Proof state:
case h2
R : Type u_1
A : Type u_2
B : Type u_3
inst✝¹² : CommSemiring R
inst✝¹¹ : StarRing R
inst✝¹⁰ : NonUnitalSemiring A
inst✝⁹ : StarRing A
inst✝⁸ : Module R A
inst✝⁷ : SMulCommClass R A A
inst✝⁶ : IsScalarTower R A A
inst✝⁵ : NonUnitalSemiring B
inst✝⁴ : StarRing B
inst✝³ : Module R B
inst✝² : SMulCommClass R B B
inst✝¹ : IsScalarTower R B B
inst✝ : StarModule R B
φ : A →⋆ₙₐ[R] B
hφ : Function.Injective ⇑φ
x y : Unitization R A
h : (starMap φ) x = (starMap φ) y
⊢ x.snd = y.snd

Tactic:
exact hφ <| by simpa [algebraMap_eq_inl] using congr(snd $(h))

Result:
no goals