case inl c_eq =>
  subst c_eq
  if φ = φ'
  then simp_all
  else aesop
L R : Finset Formula
c : TNode
φ ψ φ' ψ' : Formula
L_cond_in : {~(φ'⋀ψ')} ⊆ L
α_in_L : ~(φ⋀ψ) ∈ L
c_eq : (insert (~φ') (L.erase (~(φ'⋀ψ'))), R) = c
⊢ ~(φ⋀ψ) ∈ c.1 ∨ ~φ ∈ c.1 ∨ ~ψ ∈ c.1
no goals