Solution
= Solution
Taking the coefficient of $i$ in the expansion from part (a), the <imaginary part> is
$$
\boxed{\operatorname{Im}f=e^{-y}(x\sin x+y\cos x)}.
$$
= Solution
Taking the coefficient of $i$ in the expansion from part (a), the <imaginary part> is
$$
\boxed{\operatorname{Im}f=e^{-y}(x\sin x+y\cos x)}.
$$