rfl
D : Type
I : Interpretation D
E : Env
v t : VarName
F F' : Formula
h1_x : VarName
h1_phi : Formula
h1_v h1_t : VarName
h1_phi' : Formula
h1_1 : ¬h1_v = h1_x ∧ isFreeIn h1_v h1_phi
h1_2 : ¬h1_x = h1_t
a✝¹ : IsSub h1_phi h1_v h1_t h1_phi'
V : VarAssignment D
d : D
h1_ih :
  Holds D I (Function.updateITE (Function.updateITE V h1_x d) h1_v (Function.updateITE V h1_x d h1_t)) E h1_phi ↔
    Holds D I (Function.updateITE V h1_x d) E h1_phi'
x : VarName
a✝ : isFreeIn x h1_phi
h✝¹ : ¬h1_x = x
h✝ : ¬h1_v = x
⊢ V x = V x
no goals