Theorem: Matroid.rFin.insert (Matroid/Rank.lean)

State before:
α : Type u_1
ι : Type u_2
M N : Matroid α
I B X X' Y Y' Z R : Set α
n : ℕ∞
e✝ f : α
hX : M.rFin X
e : α
⊢ M.rFin (Insert.insert e X)
Tactic:
rw [← union_singleton]
State after:
α : Type u_1
ι : Type u_2
M N : Matroid α
I B X X' Y Y' Z R : Set α
n : ℕ∞
e✝ f : α
hX : M.rFin X
e : α
⊢ M.rFin (X ∪ {e})

State before:
α : Type u_1
ι : Type u_2
M N : Matroid α
I B X X' Y Y' Z R : Set α
n : ℕ∞
e✝ f : α
hX : M.rFin X
e : α
⊢ M.rFin (X ∪ {e})
Tactic:
exact hX.union (M.rFin_singleton e)
State after:
no goals