Theorem: Matroid.Base.ncard (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
hB : M.Base B
⊢ B.ncard = M.rk
Tactic:
rw [rk_def, ← er_toNat_eq_r, ncard_def, hB.encard, erk_eq_er_ground]
State after:
no goals