simp [subset_iUnion]
α : Type u_1
ι✝ : Type u_2
M : Matroid α
F I J X Y B C R : Set α
e f x y : α
ι : Type u_3
hι : Nonempty ι
Is : ι → Set α
h : M.Indep (⋃ i, Is i)
⊢ ∀ J ∈ range Is, J ⊆ ⋃ i, Is i
no goals