rw [disconEval (XS ⊎ YS)]
XS YS : List (List Formula)
W : Type
M : KripkeModel W
w : W
⊢ evaluate M w (discon (XS⊎YS)) ↔ evaluate M w (discon XS⋀discon YS)
XS YS : List (List Formula)
W : Type
M : KripkeModel W
w : W
⊢ (∃ Y ∈ XS⊎YS, ∀ f ∈ Y, evaluate M w f) ↔ evaluate M w (discon XS⋀discon YS)