intro x hx
L : Language
Δ✝ Δ₁ Δ₂ Γ : Sequent L
p✝ q r : SyntacticFormula L
m : ℕ
Δ : Sequent L
h : ∀ p ∈ Δ, ¬fvar? p m
p : Semiformula L ℕ 0
hp : p ∈ Δ
⊢ Function.funEqOn p.fvar? (⇑(Rew.rewriteMap fun x => if x = m then 0 else x + 1) ∘ Semiterm.fvar) (⇑⇑ ∘ Semiterm.fvar)
L : Language
Δ✝ Δ₁ Δ₂ Γ : Sequent L
p✝ q r : SyntacticFormula L
m : ℕ
Δ : Sequent L
h : ∀ p ∈ Δ, ¬fvar? p m
p : Semiformula L ℕ 0
hp : p ∈ Δ
x : ℕ
hx : p.fvar? x
⊢ (⇑(Rew.rewriteMap fun x => if x = m then 0 else x + 1) ∘ Semiterm.fvar) x = (⇑⇑ ∘ Semiterm.fvar) x