\ANG{
Beweise:\quad $\D\int x^{2}\cos ax\,\RMd x=\frac{2x}{a^{2}}\cos ax+
\left(\frac{x^{2}}{a}-\frac{2}{a^{3}}\right)\sin ax+C$
} 
\LSG{
\begin{multline*}
\frac{\RMd}{\RMd x}\left[\frac{2x}{a^{2}}\cos ax+
 \left(\frac{x^{2}}{a}-\frac{2}{a^{3}}\right)\sin ax+C \right] =\\
  \frac{2}{a^{2}}\cos ax-\frac{2x}{a}\sin ax+
   \frac{2x}{a}\sin ax+
    \left(x^{2}-\frac{2}{a^{2}}\right)\cos ax=x^{2}\cos ax\quad\text{q.e.d}
\end{multline*}

}
