Solution
= Solution
Use the <symmetric difference> formula from part (b), followed by the <set difference> identity from part (c)(ii):
$$
\begin{aligned}
\overline A\oplus\overline B
&=(\overline A\setminus\overline B)\cup(\overline B\setminus\overline A)\\
&=(B\setminus A)\cup(A\setminus B)
=A\oplus B.
\end{aligned}
$$
Taking both <complements> swaps the two ways to belong to exactly one <set>, leaving their <union> unchanged:
$$
\boxed{\overline A\oplus\overline B=A\oplus B.}
$$