x \/ bottom ≡ x
x /\ bottom ≡⟨ identity ⟩ (x /\ bottom) \/ bottom ≡⟨ absorption ⟩ bottom
x /\ top ≡ x
x \/ top ≡⟨ identity ⟩ (x \/ top) /\ top ≡⟨ absorption ⟩ top