apply ih
case cons.inl
α : Type u_1
inst✝ : DecidableEq α
x y : α
as : List α
z : α
zs : List α
ih : ∀ (cs : List α), length (uniqueAux zs (cs ++ x :: (as ++ [y]))) = length (uniqueAux zs (cs ++ y :: x :: as))
cs : List α
rearrange_mem : z ∈ cs ++ x :: (as ++ [y]) ↔ z ∈ cs ++ y :: x :: as
hin : z ∈ cs ++ x :: (as ++ [y])
⊢ length (uniqueAux zs (cs ++ x :: (as ++ [y]))) = length (uniqueAux zs (cs ++ y :: x :: as))
no goals