apply Exists.elim a1
α : Type
L : Language α
n : ℕ
ih : ∀ s ∈ exp L n, s ∈ kleene_closure α L
s : Str α
a1 : ∃ s_1 ∈ exp L n, ∃ t ∈ L, s_1 ++ t = s
⊢ s ∈ kleene_closure α L
α : Type
L : Language α
n : ℕ
ih : ∀ s ∈ exp L n, s ∈ kleene_closure α L
s : Str α
a1 : ∃ s_1 ∈ exp L n, ∃ t ∈ L, s_1 ++ t = s
⊢ ∀ (a : Str α), (a ∈ exp L n ∧ ∃ t ∈ L, a ++ t = s) → s ∈ kleene_closure α L