case ncon φ' ψ' =>
  simp at c_in
  subst precond_eq
  cases c_in
  case inl c_eq =>
    subst c_eq
    if φ = φ'
    then simp_all
    else aesop
  case inr c_eq =>
    subst c_eq
    if ψ = ψ'
    then simp_all
    else aesop
α : Formula
L R : Finset Formula
α_in_L : α ∈ L
c : TNode
φ ψ : Formula
precond_eq : ~(φ⋀ψ) = α
φ' ψ' : Formula
L_cond_in : {~(φ'⋀ψ')} ⊆ L
c_in : ∃ a ∈ [{~φ'}, {~ψ'}], (L \ {~(φ'⋀ψ')} ∪ a, R) = c
⊢ α ∈ c.1 ∨ ~φ ∈ c.1 ∨ ~ψ ∈ c.1
no goals