use h
case h.mpr
V : Type u
E : Type v
inst✝¹ : DecidableEq V
inst✝ : DecidableEq E
G : Graph V E
x₀ : V
H : Subgroup (π₁ G x₀)
x : π₁ G x₀
l : x ∈ H ↔
  ∃ h',
    x =
      (Morphism.π₁map (basepoint H) x₀ (groupCoverProj H)
          (_ : (groupCoverProj H).toFuncV (basepoint H) = (groupCoverProj H).toFuncV (basepoint H)))
        h' :=
  proj_image H x
g : x ∈ H
h : π₁ (groupCover H) (basepoint H)
heq :
  x =
    (Morphism.π₁map (basepoint H) x₀ (groupCoverProj H)
        (_ : (groupCoverProj H).toFuncV (basepoint H) = (groupCoverProj H).toFuncV (basepoint H)))
      h
⊢ ∃ x_1,
    (Morphism.π₁map (basepoint H) x₀ (groupCoverProj H)
          (_ : (groupCoverProj H).toFuncV (basepoint H) = (groupCoverProj H).toFuncV (basepoint H)))
        x_1 =
      x
case h
V : Type u
E : Type v
inst✝¹ : DecidableEq V
inst✝ : DecidableEq E
G : Graph V E
x₀ : V
H : Subgroup (π₁ G x₀)
x : π₁ G x₀
l : x ∈ H ↔
  ∃ h',
    x =
      (Morphism.π₁map (basepoint H) x₀ (groupCoverProj H)
          (_ : (groupCoverProj H).toFuncV (basepoint H) = (groupCoverProj H).toFuncV (basepoint H)))
        h' :=
  proj_image H x
g : x ∈ H
h : π₁ (groupCover H) (basepoint H)
heq :
  x =
    (Morphism.π₁map (basepoint H) x₀ (groupCoverProj H)
        (_ : (groupCoverProj H).toFuncV (basepoint H) = (groupCoverProj H).toFuncV (basepoint H)))
      h
⊢ (Morphism.π₁map (basepoint H) x₀ (groupCoverProj H)
        (_ : (groupCoverProj H).toFuncV (basepoint H) = (groupCoverProj H).toFuncV (basepoint H)))
      h =
    x