rw [get_eq_getElem]
α : Type u_1
as : Array α
i j : Fin as.size
⊢ as.get i = as[↑i]

case a
α : Type u_1
as : Array α
i j : Fin as.size
⊢ ↑(⋯ ▸ j) = ↑j
case a
α : Type u_1
as : Array α
i j : Fin as.size
⊢ ↑(⋯ ▸ j) = ↑j