exact hB.indep.subset (union_subset hIB (hK.trans fun e he ↦ Coloop.mem_of_base he hB))
case intro.intro
α : Type u_1
β : Type u_2
M N : Matroid α
e f : α
B✝ L L' I X Y Z F C K : Set α
hK : K ⊆ M✶.cl ∅
h : M.Indep I
B : Set α
hB : M.Base B
hIB : I ⊆ B
⊢ M.Indep (I ∪ K)
no goals