Pomoc� poznatk� o Riemannov� integr�lu doka�te:
$$
\lim_{n\to\infty}\Big(\frac{n}{n^2+1^2}+
\frac{n}{n^2+2^2}+ \cdots + \frac{n}{n^2+n^2}\Big)=\frac{\pi}{4}\ .
$$
