Re: Derivative of a sum.

• To: mathgroup at smc.vnet.net
• Subject: [mg101651] Re: Derivative of a sum.
• From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
• Date: Sun, 12 Jul 2009 06:57:12 -0400 (EDT)
• References: <h390no\$jri\$1@smc.vnet.net>

```I seem to have some difficulties interpreting your question.
Your summing over i but there's now i in the summand, or this (in i)
must mean something. And the derivative is with respect to which
variable?

Cheers -- Sjoerd

On Jul 11, 5:25 am, "Muntoni Giampaolo" <muntoni.gia... at alice.it>
wrote:
> In order to resolve a problem I have found the question of derivating  =
the
> expression e^(-x)*Sum(in i)(x^n/n!, (i,0,n));the solution is easy and is
> e^(-x)(x^n/n!).
> But using language of Mathematica I have obteined a different result with=
a
> ricorse of Gamma function...also recurring to the option of manipulate,
> changing the value of  integer n.
> I would want to obtain the exact result with language of Mathematica and
> Manipulate respect to n and also plotting the original function and its
> derivative.(with manipulate)
> Thanks for aids
> Giampaolo

```

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