simp [← inter_iUnion, hCU, Subset.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
hXs : ∀ (i : ι), Xs i ⊆ M.E
hdj : Pairwise (Disjoint on Xs)
h : M.SkewFamily Xs
C : Set α
hC : M.Circuit C
hCU : C ⊆ ⋃ i, Xs i
hcon : ∀ (i : ι), M.Indep (C ∩ Xs i)
⊢ C ⊆ ⋃ i, C ∩ Xs i
no goals