\[(-1)^{\left\lfloor(n+1)/2\right\rfloor}\frac{\pi^{n+1}}{4(n!)}E_{n}\left(x%
\right)\to\begin{cases}\sin\left(\pi x\right),&n\text{ even},\\
\cos\left(\pi x\right),&n\text{ odd},\end{cases}\]