-- Mathlib/Geometry/Manifold/VectorBundle/Basic.lean
theorem contMDiffVectorBundle : @ContMDiffVectorBundle n
    _ _ F E _ _ _ _ _ _ IB _ _ _ _ _ _ a.totalSpaceTopology _ a.toFiberBundle a.toVectorBundle :=
  letI := a.totalSpaceTopology; letI := a.toFiberBundle; letI := a.toVectorBundle
  { contMDiffOn_coordChangeL

Proof state:
case mk.intro.intro.mk.intro.intro.h
n : WithTop ℕ∞
𝕜 : Type u_1
B : Type u_2
F : Type u_4
E : B → Type u_6
inst✝¹⁰ : NontriviallyNormedField 𝕜
EB : Type u_7
inst✝⁹ : NormedAddCommGroup EB
inst✝⁸ : NormedSpace 𝕜 EB
HB : Type u_8
inst✝⁷ : TopologicalSpace HB
IB : ModelWithCorners 𝕜 EB HB
inst✝⁶ : TopologicalSpace B
inst✝⁵ : ChartedSpace HB B
inst✝⁴ : (x : B) → AddCommMonoid (E x)
inst✝³ : (x : B) → Module 𝕜 (E x)
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace 𝕜 F
inst✝ : (x : B) → TopologicalSpace (E x)
a : VectorPrebundle 𝕜 F E
ha : IsContMDiff IB a n
this✝¹ : TopologicalSpace (TotalSpace F E) := a.totalSpaceTopology
this✝ : FiberBundle F E := a.toFiberBundle
this : VectorBundle 𝕜 F E := toVectorBundle a
e : Pretrivialization F TotalSpace.proj
he : e ∈ a.toFiberPrebundle.pretrivializationAtlas
e' : Pretrivialization F TotalSpace.proj
he' : e' ∈ a.toFiberPrebundle.pretrivializationAtlas
b : B
hb : b ∈ e.baseSet ∩ e'.baseSet
v : F
⊢ ↑(Trivialization.coordChangeL 𝕜 (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he)
          (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he') b)
      v =
    (contMDiffCoordChange n IB a he he' b) v

Tactic:
rw [a.contMDiffCoordChange_apply he he' hb v, ContinuousLinearEquiv.coe_coe,
  Trivialization.coordChangeL_apply]

Result:
case mk.intro.intro.mk.intro.intro.h
n : WithTop ℕ∞
𝕜 : Type u_1
B : Type u_2
F : Type u_4
E : B → Type u_6
inst✝¹⁰ : NontriviallyNormedField 𝕜
EB : Type u_7
inst✝⁹ : NormedAddCommGroup EB
inst✝⁸ : NormedSpace 𝕜 EB
HB : Type u_8
inst✝⁷ : TopologicalSpace HB
IB : ModelWithCorners 𝕜 EB HB
inst✝⁶ : TopologicalSpace B
inst✝⁵ : ChartedSpace HB B
inst✝⁴ : (x : B) → AddCommMonoid (E x)
inst✝³ : (x : B) → Module 𝕜 (E x)
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace 𝕜 F
inst✝ : (x : B) → TopologicalSpace (E x)
a : VectorPrebundle 𝕜 F E
ha : IsContMDiff IB a n
this✝¹ : TopologicalSpace (TotalSpace F E) := a.totalSpaceTopology
this✝ : FiberBundle F E := a.toFiberBundle
this : VectorBundle 𝕜 F E := toVectorBundle a
e : Pretrivialization F TotalSpace.proj
he : e ∈ a.toFiberPrebundle.pretrivializationAtlas
e' : Pretrivialization F TotalSpace.proj
he' : e' ∈ a.toFiberPrebundle.pretrivializationAtlas
b : B
hb : b ∈ e.baseSet ∩ e'.baseSet
v : F
⊢ (↑(a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he')
        { proj := b, snd := (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he).symm b v }).2 =
    (↑e' { proj := b, snd := e.symm b v }).2

case mk.intro.intro.mk.intro.intro.h.hb
n : WithTop ℕ∞
𝕜 : Type u_1
B : Type u_2
F : Type u_4
E : B → Type u_6
inst✝¹⁰ : NontriviallyNormedField 𝕜
EB : Type u_7
inst✝⁹ : NormedAddCommGroup EB
inst✝⁸ : NormedSpace 𝕜 EB
HB : Type u_8
inst✝⁷ : TopologicalSpace HB
IB : ModelWithCorners 𝕜 EB HB
inst✝⁶ : TopologicalSpace B
inst✝⁵ : ChartedSpace HB B
inst✝⁴ : (x : B) → AddCommMonoid (E x)
inst✝³ : (x : B) → Module 𝕜 (E x)
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace 𝕜 F
inst✝ : (x : B) → TopologicalSpace (E x)
a : VectorPrebundle 𝕜 F E
ha : IsContMDiff IB a n
this✝¹ : TopologicalSpace (TotalSpace F E) := a.totalSpaceTopology
this✝ : FiberBundle F E := a.toFiberBundle
this : VectorBundle 𝕜 F E := toVectorBundle a
e : Pretrivialization F TotalSpace.proj
he : e ∈ a.toFiberPrebundle.pretrivializationAtlas
e' : Pretrivialization F TotalSpace.proj
he' : e' ∈ a.toFiberPrebundle.pretrivializationAtlas
b : B
hb : b ∈ e.baseSet ∩ e'.baseSet
v : F
⊢ b ∈
    (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he).baseSet ∩
      (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he').baseSet

Proof state:
case mk.intro.intro.mk.intro.intro.h
n : WithTop ℕ∞
𝕜 : Type u_1
B : Type u_2
F : Type u_4
E : B → Type u_6
inst✝¹⁰ : NontriviallyNormedField 𝕜
EB : Type u_7
inst✝⁹ : NormedAddCommGroup EB
inst✝⁸ : NormedSpace 𝕜 EB
HB : Type u_8
inst✝⁷ : TopologicalSpace HB
IB : ModelWithCorners 𝕜 EB HB
inst✝⁶ : TopologicalSpace B
inst✝⁵ : ChartedSpace HB B
inst✝⁴ : (x : B) → AddCommMonoid (E x)
inst✝³ : (x : B) → Module 𝕜 (E x)
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace 𝕜 F
inst✝ : (x : B) → TopologicalSpace (E x)
a : VectorPrebundle 𝕜 F E
ha : IsContMDiff IB a n
this✝¹ : TopologicalSpace (TotalSpace F E) := a.totalSpaceTopology
this✝ : FiberBundle F E := a.toFiberBundle
this : VectorBundle 𝕜 F E := toVectorBundle a
e : Pretrivialization F TotalSpace.proj
he : e ∈ a.toFiberPrebundle.pretrivializationAtlas
e' : Pretrivialization F TotalSpace.proj
he' : e' ∈ a.toFiberPrebundle.pretrivializationAtlas
b : B
hb : b ∈ e.baseSet ∩ e'.baseSet
v : F
⊢ (↑(a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he')
        { proj := b, snd := (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he).symm b v }).2 =
    (↑e' { proj := b, snd := e.symm b v }).2

case mk.intro.intro.mk.intro.intro.h.hb
n : WithTop ℕ∞
𝕜 : Type u_1
B : Type u_2
F : Type u_4
E : B → Type u_6
inst✝¹⁰ : NontriviallyNormedField 𝕜
EB : Type u_7
inst✝⁹ : NormedAddCommGroup EB
inst✝⁸ : NormedSpace 𝕜 EB
HB : Type u_8
inst✝⁷ : TopologicalSpace HB
IB : ModelWithCorners 𝕜 EB HB
inst✝⁶ : TopologicalSpace B
inst✝⁵ : ChartedSpace HB B
inst✝⁴ : (x : B) → AddCommMonoid (E x)
inst✝³ : (x : B) → Module 𝕜 (E x)
inst✝² : NormedAddCommGroup F
inst✝¹ : NormedSpace 𝕜 F
inst✝ : (x : B) → TopologicalSpace (E x)
a : VectorPrebundle 𝕜 F E
ha : IsContMDiff IB a n
this✝¹ : TopologicalSpace (TotalSpace F E) := a.totalSpaceTopology
this✝ : FiberBundle F E := a.toFiberBundle
this : VectorBundle 𝕜 F E := toVectorBundle a
e : Pretrivialization F TotalSpace.proj
he : e ∈ a.toFiberPrebundle.pretrivializationAtlas
e' : Pretrivialization F TotalSpace.proj
he' : e' ∈ a.toFiberPrebundle.pretrivializationAtlas
b : B
hb : b ∈ e.baseSet ∩ e'.baseSet
v : F
⊢ b ∈
    (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he).baseSet ∩
      (a.toFiberPrebundle.trivializationOfMemPretrivializationAtlas he').baseSet

Tactic:
exacts [rfl, hb]

Result:
no goals