Riemann zeta function evaluated at 2, Sum of p series when p = 2, Basel Problem and Euler’s product formula:
Buffon’s needle problem:
If a short needle, of length, is dropped on paper that is ruled with equally spaced lines of distance
, then the probability that the needle comes to lie in a position where it crosses one of the lines is exactly


![Rendered by QuickLaTeX.com \[ e^{i \pi} + 1 = 0 \]](http://www.vijaykandy.com/wp-content/ql-cache/quicklatex.com-51f9c4fbabd19ada1908ba51b8da3add_l3.png)
![Rendered by QuickLaTeX.com \[ \zeta(2) = \left \displaystyle\sum_{n=1}^{\infty}\frac{1}{n^2} = \prod_{p \text{ prime}} \frac{1}{1-p^{-2}} = \frac{\pi^2}{6} \]](http://www.vijaykandy.com/wp-content/ql-cache/quicklatex.com-38235c8c6e0a61034a34effefd7111a1_l3.png)
, is dropped on paper that is ruled with equally spaced lines of distance
, then the probability that the needle comes to lie in a position where it crosses one of the lines is exactly![Rendered by QuickLaTeX.com \[ \frac{2 l}{\pi d} \]](http://www.vijaykandy.com/wp-content/ql-cache/quicklatex.com-50592c9439ffd1ab593960863ef60561_l3.png)