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MathGroup Archive 2006

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Re: Problem with derivate of product

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67315] Re: Problem with derivate of product
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sun, 18 Jun 2006 05:13:00 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <e70fid$rmp$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Esa A E Peuha wrote:
> Mathematica 5.0 seems to have trouble with parsing this input:
> 
> In[1]:= D[Product[f[k,z],{k,0,m}],{z,n}]
> 
> Out[1]= D[Product[f[k, z], {k, 0, m}], z]
> 
> Has this been fixed in newer versions?
> 
What output do you expect? Since f is not defined, the product is 
returned unevaluated:

In[2]:=
Product[f[k, z], {k, 0, m}]

Out[2]=
Product[f[k, z], {k, 0, m}]

Compare with

In[5]:=
f[a_, b_] := b*Cos[a]

In[6]:=
Product[f[k, z], {k, 0, 2}]

Out[6]=
  3
z  Cos[1] Cos[2]

In[7]:=
D[Product[f[k, z], {k, 0, 2}], {z, 1}]

Out[7]=
    2
3 z  Cos[1] Cos[2]

HTH,
Jean-Marc


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