Theorem: Matroid.Cocircuit.of_contract (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
hK : (M ／ C).Cocircuit K
⊢ M.Cocircuit K
Tactic:
rw [cocircuit_def, contract_dual_eq_dual_delete] at hK
State after:
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
hK : (M✶ ＼ C).Circuit K
⊢ M.Cocircuit K

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
hK : (M✶ ＼ C).Circuit K
⊢ M.Cocircuit K
Tactic:
exact hK.of_delete
State after:
no goals