Theorem: Matroid.Cocircuit.delete_diff_cocircuit (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 X : Set α
hK : M.Cocircuit K
hXK : X ⊆ K
hX : X.Nonempty
⊢ (M ＼ (K \ X)).Cocircuit X
Tactic:
rw [cocircuit_def, delete_dual_eq_dual_contract]
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 X : Set α
hK : M.Cocircuit K
hXK : X ⊆ K
hX : X.Nonempty
⊢ (M✶ ／ (K \ X)).Circuit X

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 X : Set α
hK : M.Cocircuit K
hXK : X ⊆ K
hX : X.Nonempty
⊢ (M✶ ／ (K \ X)).Circuit X
Tactic:
exact hK.circuit.contract_diff_circuit hX hXK
State after:
no goals