α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ((a ⊓ ￢a ≤ a ⊔ (a ⊔ b) ∧ a ⊓ ￢a ≤ a ⊔ ￢(a ⊔ b)) ∧ a ⊓ ￢a ≤ a ⊔ b ∧ a ⊓ ￢a ≤ ￢(a ⊔ b) ⊔ b) ∧
    a ⊓ ￢a ≤ a ⊔ (b ⊔ ￢(a ⊓ b)) ∧ a ⊓ ￢a ≤ ￢(a ⊔ b) ⊔ ￢(a ⊓ b)
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ∂ a ≤ ∂ (a ⊔ b) ⊔ ∂ (a ⊓ b)
simp only [boundary, sup_inf_left, sup_inf_right, sup_right_idem, le_inf_iff, sup_assoc,
  @sup_comm _ _ _ a]
case refine_4
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ￢a ≤ ￢(a ⊔ b) ⊔ b

case refine_6
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ￢a ≤ ￢(a ⊔ b) ⊔ ￢(a ⊓ b)
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ((a ⊓ ￢a ≤ a ⊔ (a ⊔ b) ∧ a ⊓ ￢a ≤ a ⊔ ￢(a ⊔ b)) ∧ a ⊓ ￢a ≤ a ⊔ b ∧ a ⊓ ￢a ≤ ￢(a ⊔ b) ⊔ b) ∧
    a ⊓ ￢a ≤ a ⊔ (b ⊔ ￢(a ⊓ b)) ∧ a ⊓ ￢a ≤ ￢(a ⊔ b) ⊔ ￢(a ⊓ b)
refine ⟨⟨⟨?_, ?_⟩, ⟨?_, ?_⟩⟩, ?_, ?_⟩ <;> try { exact le_sup_of_le_left inf_le_left } <;>
  refine inf_le_of_right_le ?_
case refine_4
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ Codisjoint (￢(a ⊔ b)) (a ⊔ b)
case refine_4
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ￢a ≤ ￢(a ⊔ b) ⊔ b
rw [hnot_le_iff_codisjoint_right, codisjoint_left_comm]
no goals
case refine_4
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ Codisjoint (￢(a ⊔ b)) (a ⊔ b)
exact codisjoint_hnot_left
case refine_6
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ￢a ≤ ￢(a ⊓ b)
case refine_6
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ￢a ≤ ￢(a ⊔ b) ⊔ ￢(a ⊓ b)
refine le_sup_of_le_right ?_
case refine_6
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ Codisjoint a (￢(a ⊓ b))
case refine_6
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ ￢a ≤ ￢(a ⊓ b)
rw [hnot_le_iff_codisjoint_right]
no goals
case refine_6
α : Type u_1
inst✝ : CoheytingAlgebra α
a b : α
⊢ Codisjoint a (￢(a ⊓ b))
exact codisjoint_hnot_right.mono_right (hnot_anti inf_le_left)