# Math Help - Limit of Sequence

1. ## Limit of Sequence

find the limit of the sequence :

$
\lim_{x\to \infty}(cos\frac{x}{2}cos\frac{x}{4}...cos\frac{x} {2^n})$

2. In this question do you mean
$\displaystyle \lim_{n\to \infty}\text{ or }\lim_{x\to \infty}~?$

3. sorry
it's $\lim_{n\to \infty}$

4. I believe what you ask about is know as Viète's infinite product

see List of trigonometric identities - Wikipedia, the free encyclopedia

a little more than half way down.