Re: Derivative of a sum.
- To: mathgroup at smc.vnet.net
- Subject: [mg101632] Re: [mg101615] Derivative of a sum.
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sun, 12 Jul 2009 05:48:35 -0400 (EDT)
- Reply-to: hanlonr at cox.net
Presumably you meant the sum to be
f[x_, n_] = E^(-x)*Sum[x^i/i!, {i, 0, n}]
Gamma[n + 1, x]/n!
fp[x_, n_] = D[f[x, n], x]
-(x^n/(E^x*n!))
Manipulate[
Plot[{
Tooltip[f[x, n], "f"],
Tooltip[fp[x, n], "fp"]},
{x, 0, 5},
PlotRange -> {-1, 1}],
{n, 0, 4, Appearance -> "Labeled"}]
Bob Hanlon
---- Muntoni Giampaolo <muntoni.giampa 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