-- Mathlib/Algebra/Category/ModuleCat/Presheaf/Sheafify.lean
protected lemma zero_smul : smul α φ 0 m = 0

Proof state:
case a
C : Type u₁
inst✝⁴ : Category.{v₁, u₁} C
J : GrothendieckTopology C
R₀ : Cᵒᵖ ⥤ RingCat
R : Sheaf J RingCat
α : R₀ ⟶ R.val
inst✝³ : Presheaf.IsLocallyInjective J α
inst✝² : Presheaf.IsLocallySurjective J α
M₀ : PresheafOfModules R₀
A : Sheaf J AddCommGrp
φ : M₀.presheaf ⟶ A.val
inst✝¹ : Presheaf.IsLocallyInjective J φ
inst✝ : Presheaf.IsLocallySurjective J φ
X : Cᵒᵖ
m : ↑(A.val.obj X)
⊢ ∀ (Y : C) (f : Y ⟶ Opposite.unop X),
    (Presheaf.imageSieve φ m).arrows f →
      (ConcreteCategory.hom (A.val.map f.op)) (smul α φ 0 m) = (ConcreteCategory.hom (A.val.map f.op)) 0

Tactic:
rintro Y f ⟨m₀, hm₀⟩

Result:
case a.intro
C : Type u₁
inst✝⁴ : Category.{v₁, u₁} C
J : GrothendieckTopology C
R₀ : Cᵒᵖ ⥤ RingCat
R : Sheaf J RingCat
α : R₀ ⟶ R.val
inst✝³ : Presheaf.IsLocallyInjective J α
inst✝² : Presheaf.IsLocallySurjective J α
M₀ : PresheafOfModules R₀
A : Sheaf J AddCommGrp
φ : M₀.presheaf ⟶ A.val
inst✝¹ : Presheaf.IsLocallyInjective J φ
inst✝ : Presheaf.IsLocallySurjective J φ
X : Cᵒᵖ
m : ↑(A.val.obj X)
Y : C
f : Y ⟶ Opposite.unop X
m₀ : ToType (M₀.presheaf.obj (Opposite.op Y))
hm₀ : (ConcreteCategory.hom (φ.app (Opposite.op Y))) m₀ = (ConcreteCategory.hom (A.val.map f.op)) m
⊢ (ConcreteCategory.hom (A.val.map f.op)) (smul α φ 0 m) = (ConcreteCategory.hom (A.val.map f.op)) 0

Proof state:
case a.intro
C : Type u₁
inst✝⁴ : Category.{v₁, u₁} C
J : GrothendieckTopology C
R₀ : Cᵒᵖ ⥤ RingCat
R : Sheaf J RingCat
α : R₀ ⟶ R.val
inst✝³ : Presheaf.IsLocallyInjective J α
inst✝² : Presheaf.IsLocallySurjective J α
M₀ : PresheafOfModules R₀
A : Sheaf J AddCommGrp
φ : M₀.presheaf ⟶ A.val
inst✝¹ : Presheaf.IsLocallyInjective J φ
inst✝ : Presheaf.IsLocallySurjective J φ
X : Cᵒᵖ
m : ↑(A.val.obj X)
Y : C
f : Y ⟶ Opposite.unop X
m₀ : ToType (M₀.presheaf.obj (Opposite.op Y))
hm₀ : (ConcreteCategory.hom (φ.app (Opposite.op Y))) m₀ = (ConcreteCategory.hom (A.val.map f.op)) m
⊢ (ConcreteCategory.hom (A.val.map f.op)) (smul α φ 0 m) = (ConcreteCategory.hom (A.val.map f.op)) 0

Tactic:
rw [map_smul_eq α φ 0 m f.op 0 (by simp) m₀ hm₀, zero_smul, map_zero,
  (A.val.map f.op).hom.map_zero]

Result:
no goals

Proof state:
C : Type u₁
inst✝⁴ : Category.{v₁, u₁} C
J : GrothendieckTopology C
R₀ : Cᵒᵖ ⥤ RingCat
R : Sheaf J RingCat
α : R₀ ⟶ R.val
inst✝³ : Presheaf.IsLocallyInjective J α
inst✝² : Presheaf.IsLocallySurjective J α
M₀ : PresheafOfModules R₀
A : Sheaf J AddCommGrp
φ : M₀.presheaf ⟶ A.val
inst✝¹ : Presheaf.IsLocallyInjective J φ
inst✝ : Presheaf.IsLocallySurjective J φ
X : Cᵒᵖ
m : ↑(A.val.obj X)
Y : C
f : Y ⟶ Opposite.unop X
m₀ : ToType (M₀.presheaf.obj (Opposite.op Y))
hm₀ : (ConcreteCategory.hom (φ.app (Opposite.op Y))) m₀ = (ConcreteCategory.hom (A.val.map f.op)) m
⊢ (ConcreteCategory.hom (α.app (Opposite.op Y))) 0 = (ConcreteCategory.hom (R.val.map f.op)) 0

Tactic:
simp

Result:
no goals

Proof state:
C : Type u₁
inst✝⁴ : Category.{v₁, u₁} C
J : GrothendieckTopology C
R₀ : Cᵒᵖ ⥤ RingCat
R : Sheaf J RingCat
α : R₀ ⟶ R.val
inst✝³ : Presheaf.IsLocallyInjective J α
inst✝² : Presheaf.IsLocallySurjective J α
M₀ : PresheafOfModules R₀
A : Sheaf J AddCommGrp
φ : M₀.presheaf ⟶ A.val
inst✝¹ : Presheaf.IsLocallyInjective J φ
inst✝ : Presheaf.IsLocallySurjective J φ
X : Cᵒᵖ
m : ↑(A.val.obj X)
⊢ smul α φ 0 m = 0

Tactic:
apply A.isSeparated _ _ (Presheaf.imageSieve_mem J φ m)

Result:
case a
C : Type u₁
inst✝⁴ : Category.{v₁, u₁} C
J : GrothendieckTopology C
R₀ : Cᵒᵖ ⥤ RingCat
R : Sheaf J RingCat
α : R₀ ⟶ R.val
inst✝³ : Presheaf.IsLocallyInjective J α
inst✝² : Presheaf.IsLocallySurjective J α
M₀ : PresheafOfModules R₀
A : Sheaf J AddCommGrp
φ : M₀.presheaf ⟶ A.val
inst✝¹ : Presheaf.IsLocallyInjective J φ
inst✝ : Presheaf.IsLocallySurjective J φ
X : Cᵒᵖ
m : ↑(A.val.obj X)
⊢ ∀ (Y : C) (f : Y ⟶ Opposite.unop X),
    (Presheaf.imageSieve φ m).arrows f →
      (ConcreteCategory.hom (A.val.map f.op)) (smul α φ 0 m) = (ConcreteCategory.hom (A.val.map f.op)) 0