-- Mathlib/Geometry/Manifold/WhitneyEmbedding.lean
theorem exists_immersion_euclidean {ι : Type*} [Finite ι] (f : SmoothBumpCovering ι I M) :
    ∃ (n : ℕ) (e : M → EuclideanSpace ℝ (Fin n)),
      ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ x : M, Injective (mfderiv I (𝓡 n) e x)

Proof state:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this✝ : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
this : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.mp inferInstance
eEF : (ι → E × ℝ) ≃L[ℝ] F := ContinuousLinearEquiv.ofFinrankEq ⋯
x : M
⊢ Injective ⇑(mfderiv I (𝓡 finrank ℝ (ι → E × ℝ)) (⇑eEF ∘ ⇑f.embeddingPiTangent) x)

Tactic:
rw [mfderiv_comp _ eEF.differentiableAt.mdifferentiableAt
    (f.embeddingPiTangent.contMDiff.mdifferentiableAt (mod_cast le_top)),
  eEF.mfderiv_eq]

Result:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this✝ : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
this : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.mp inferInstance
eEF : (ι → E × ℝ) ≃L[ℝ] F := ContinuousLinearEquiv.ofFinrankEq ⋯
x : M
⊢ Injective ⇑((↑eEF).comp (mfderiv I 𝓘(ℝ, ι → E × ℝ) (⇑f.embeddingPiTangent) x))

Proof state:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this✝ : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
this : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.mp inferInstance
⊢ ∃ n e, ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ (x : M), Injective ⇑(mfderiv I (𝓡 n) e x)

Tactic:
set eEF : (ι → E × ℝ) ≃L[ℝ] F :=
  ContinuousLinearEquiv.ofFinrankEq finrank_euclideanSpace_fin.symm

Result:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this✝ : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
this : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.mp inferInstance
eEF : (ι → E × ℝ) ≃L[ℝ] F := ContinuousLinearEquiv.ofFinrankEq ⋯
⊢ ∃ n e, ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ (x : M), Injective ⇑(mfderiv I (𝓡 n) e x)

Proof state:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
⊢ ∃ n e, ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ (x : M), Injective ⇑(mfderiv I (𝓡 n) e x)

Tactic:
set F := EuclideanSpace ℝ (Fin <| finrank ℝ (ι → E × ℝ))

Result:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
⊢ ∃ n e, ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ (x : M), Injective ⇑(mfderiv I (𝓡 n) e x)

Proof state:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this✝ : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
this : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.mp inferInstance
eEF : (ι → E × ℝ) ≃L[ℝ] F := ContinuousLinearEquiv.ofFinrankEq ⋯
x : M
⊢ Injective ⇑((↑eEF).comp (mfderiv I 𝓘(ℝ, ι → E × ℝ) (⇑f.embeddingPiTangent) x))

Tactic:
exact eEF.injective.comp (f.embeddingPiTangent_injective_mfderiv _ trivial)

Result:
no goals

Proof state:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
⊢ ∃ n e, ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ (x : M), Injective ⇑(mfderiv I (𝓡 n) e x)

Tactic:
letI : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.1 inferInstance

Result:
case intro
E : Type uE
inst✝⁸ : NormedAddCommGroup E
inst✝⁷ : NormedSpace ℝ E
inst✝⁶ : FiniteDimensional ℝ E
H : Type uH
inst✝⁵ : TopologicalSpace H
I : ModelWithCorners ℝ E H
M : Type uM
inst✝⁴ : TopologicalSpace M
inst✝³ : ChartedSpace H M
inst✝² : IsManifold I ∞ M
inst✝¹ : T2Space M
ι : Type u_1
inst✝ : Finite ι
f : SmoothBumpCovering ι I M
val✝ : Fintype ι
F : Type := EuclideanSpace ℝ (Fin (finrank ℝ (ι → E × ℝ)))
this✝ : IsNoetherian ℝ (E × ℝ) := IsNoetherian.iff_fg.mpr inferInstance
this : FiniteDimensional ℝ (ι → E × ℝ) := IsNoetherian.iff_fg.mp inferInstance
⊢ ∃ n e, ContMDiff I (𝓡 n) ∞ e ∧ Injective e ∧ ∀ (x : M), Injective ⇑(mfderiv I (𝓡 n) e x)