Theorem: Matroid.erk_eq_er_ground (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
M : Matroid α
⊢ M.erk = M.er M.E
Tactic:
rw [er, restrict_ground_eq_self]
State after:
no goals