refine Finset.insert_subset_iff.mpr ?_
case h
R L : Finset Formula
φ ψ φ' ψ' : Formula
R_cond_in : φ'⋀ψ' ∈ R
α_in_R : φ⋀ψ ∈ R
h✝ : φ = φ' ∧ ψ = ψ'
⊢ {φ, ψ} ⊆ insert φ' (insert ψ' (R.erase (φ'⋀ψ')))
case h
R L : Finset Formula
φ ψ φ' ψ' : Formula
R_cond_in : φ'⋀ψ' ∈ R
α_in_R : φ⋀ψ ∈ R
h✝ : φ = φ' ∧ ψ = ψ'
⊢ φ ∈ insert φ' (insert ψ' (R.erase (φ'⋀ψ'))) ∧ {ψ} ⊆ insert φ' (insert ψ' (R.erase (φ'⋀ψ')))