Theorem: Matroid.Indep.r (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
hI : M.Indep I
⊢ M.r I = I.ncard
Tactic:
rw [← er_toNat_eq_r, hI.er, ncard_def]
State after:
no goals