$\displaystyle e^{-x}}\sum _{k=0}^{2011}{\frac {{x}^{k}}{k!}$

Thank you!

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- Dec 14th 2011, 10:10 AMgotmejerryHow can I derivate this?
$\displaystyle e^{-x}}\sum _{k=0}^{2011}{\frac {{x}^{k}}{k!}$

Thank you! - Dec 14th 2011, 10:15 AMSironRe: How can I derivate this?
Use the product rule and:

$\displaystyle \frac{d}{dx}\left(\sum_{k=0}^{2011} \frac{x^k}{k!}\right)=\sum_{k=0}^{2011} \frac{d}{dx}\left(\frac{x^k}{k!}\right)$ - Dec 14th 2011, 01:22 PMgotmejerryRe: How can I derivate this?
OKay, but i dont know how to derivate that factorial stuff

- Dec 14th 2011, 01:26 PMpickslidesRe: How can I derivate this?
You are only taking the derivative with respect to x, k! is constant.

- Dec 14th 2011, 01:47 PMgotmejerryRe: How can I derivate this?
Then it is only kx^k-1 /k!?

- Dec 14th 2011, 01:52 PMe^(i*pi)Re: How can I derivate this?
- Dec 14th 2011, 01:56 PMgotmejerryRe: How can I derivate this?
Thank you!