rw [disEval,helper] at IHβ
case mp.beta_equiv
ψ : Formula
β : Program
ρ : Formula := dis (List.map (fun Fδ => Con (Yset Fδ ψ)) (H (∗β)))
right_to_left_claim : ∀ (W : Type) (M : KripkeModel W) (w : W), evaluate M w ρ → evaluate M w (~⌈∗β⌉ψ)
x : ℕ := freshVarProg β
x_not_in : x ∉ voc β
σ0 : Formula :=
  dis
    (List.map
      (fun x =>
        match x with
        | (F, δ) => if δ = ε then Con F else ⊥)
      (H β))
σ1 : Formula :=
  dis
    (List.map
      (fun x_1 =>
        match x_1 with
        | (F, δ) => if δ ≠ ε then Con ((~⌈⌈δ⌉⌉~·x) :: F) else ⊥)
      (H β))
W : Type
M : KripkeModel W
w : W
IHβ : evaluate M w (~⌈β⌉~·x) ↔ evaluate M w (dis (List.map (fun Fδ => Con (Yset Fδ (~·x))) (H β)))
⊢ evaluate M w (~⌈β⌉~·x) ↔ evaluate M w ((·x)⋀σ0⋁σ1)
case mp.beta_equiv
ψ : Formula
β : Program
ρ : Formula := dis (List.map (fun Fδ => Con (Yset Fδ ψ)) (H (∗β)))
right_to_left_claim : ∀ (W : Type) (M : KripkeModel W) (w : W), evaluate M w ρ → evaluate M w (~⌈∗β⌉ψ)
x : ℕ := freshVarProg β
x_not_in : x ∉ voc β
σ0 : Formula :=
  dis
    (List.map
      (fun x =>
        match x with
        | (F, δ) => if δ = ε then Con F else ⊥)
      (H β))
σ1 : Formula :=
  dis
    (List.map
      (fun x_1 =>
        match x_1 with
        | (F, δ) => if δ ≠ ε then Con ((~⌈⌈δ⌉⌉~·x) :: F) else ⊥)
      (H β))
W : Type
M : KripkeModel W
w : W
IHβ : evaluate M w (~⌈β⌉~·x) ↔ ∃ Fδ ∈ H β, evaluate M w (Con (Yset Fδ (~·x)))
⊢ evaluate M w (~⌈β⌉~·x) ↔ evaluate M w ((·x)⋀σ0⋁σ1)