simp
v : VarName
phi psi : Formula
phi_ih : isFreeIn v phi ↔ v ∈ phi.freeVarSet
psi_ih : isFreeIn v psi ↔ v ∈ psi.freeVarSet
⊢ isFreeIn v phi ∨ isFreeIn v psi ↔ v ∈ phi.freeVarSet ∪ psi.freeVarSet
v : VarName
phi psi : Formula
phi_ih : isFreeIn v phi ↔ v ∈ phi.freeVarSet
psi_ih : isFreeIn v psi ↔ v ∈ psi.freeVarSet
⊢ isFreeIn v phi ∨ isFreeIn v psi ↔ v ∈ phi.freeVarSet ∨ v ∈ psi.freeVarSet