rintro e ⟨hei, heI⟩ _ hej rfl
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e f : α
h : M.SkewFamily Xs
hI : M.Indep I
hij : i ≠ j
⊢ ∀ ⦃a : α⦄, a ∈ Xs i ∩ I → ∀ ⦃b : α⦄, b ∈ Xs j → a ≠ b
case intro
ι : Type u_1
α : Type u_2
M : Matroid α
B I J X X' Y Y' F : Set α
Xs Ys Js Is : ι → Set α
i j : ι
e✝ f : α
h : M.SkewFamily Xs
hI : M.Indep I
hij : i ≠ j
e : α
hei : e ∈ Xs i
heI : e ∈ I
hej : e ∈ Xs j
⊢ False