Theorem: Matroid.contract_eq_self_iff (Matroid/Minor/Basic.lean)

State before:
α : Type u_1
M M' N : Matroid α
e f : α
I J R B X Y Z K C C₁ C₂ : Set α
⊢ M ／ C = M ↔ Disjoint C M.E
Tactic:
rw [← dual_delete_dual_eq_contract, ← dual_inj, dual_dual, delete_eq_self_iff, dual_ground]
State after:
no goals