Re: Dealing with sums
- To: mathgroup at smc.vnet.net
- Subject: [mg41000] Re: Dealing with sums
- From: bobhanlon at aol.com (Bob Hanlon)
- Date: Mon, 28 Apr 2003 02:30:04 -0400 (EDT)
- References: <b8g114$pg5$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Unprotect[D];
D[Subscript[a_, m_],
Subscript[a_, n_]] := KroneckerDelta[n-m]
Protect[D];
D[Sum[Subscript[a, i], {i, 0, n}],
Subscript[a, m]]
UnitStep[m] UnitStep[-m+n]
%//FullSimplify
UnitStep[m,-m+n]
D[Sum[Subscript[a, i], {i, 0, n}],
Subscript[a, 3]]
UnitStep[-3+n]
Bob Hanlon
In article <b8g114$pg5$1 at smc.vnet.net>, Stepan Yakovenko <yakovenko at ngs.ru>
wrote:
<<
Subject: Dealing with sums
From: Stepan Yakovenko <yakovenko at ngs.ru>
To: mathgroup at smc.vnet.net
Date: Sun, 27 Apr 2003 07:31:48 +0000 (UTC)
HI!
I want to get a derivative in terms of KroneckerDelta function:
\!\(\[PartialD]\_\(a\_3\)\(\[Sum]\+\(i = 0\)\%N a\_i\)\)
But I get 0.
Is there a way to do it in Mathematica ?
--
Best regards,
Stepan mailto:yakovenko at ngs.ru
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