Talk:Proof of Wallis product/to do


 * Move the derivation of



\frac{\sin(x)}{x} = \left(1 - \frac{x^2}{\pi^2}\right)\left(1 - \frac{x^2}{4\pi^2}\right)\left(1 - \frac{x^2}{9\pi^2}\right) \cdots $$

to Euler-Wallis formula.


 * Make some effort to justify this derivation, possibly using the PlanetMath article on the Weierstrass factorization theorem.


 * Note how to use this formula to compute



\sum_{n=1}^{\infty} \frac{1}{n^2}. $$


 * A historical account would be nice.