<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">Sečtěte řadu 
$$
\sum _{n=1}^{\infty }{\frac {\left (-1\right )^{n-1}{x}^{2\,n}}{n
\left (2\,n-1\right )}} \quad .
$$
</pre></body></html>