Re: Beginner--Error in Series expansion
- To: mathgroup at smc.vnet.net
- Subject: [mg68167] Re: [mg68155] Beginner--Error in Series expansion
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Thu, 27 Jul 2006 05:29:46 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
Z[L_]=Sum[(((-1)^Lp/(
L - Lp + 1))*(1/ksi^Lp)), {Lp, 0, L}] - (-1)^L Log[1 + ksi]/ksi^(L + 1);
devZ[L_] := Normal[Series[Z[L], {ksi, 0, 2}]]
Note use of SetDelayed vice Set in definition of devZ
devZ[3]
ksi/5 - ksi^2/6
Bob Hanlon
---- abdou.oumaima at hotmail.com wrote:
> Hello mathgroup,
>
> When I'm trying to find a power series of this function, It doesn't yield the correct expression:
>
> Z[L_] = Sum[(((-1)^Lp/(
> L - Lp + 1))*(1/ksi^Lp)), {Lp, 0, L}] - (-1)^L Log[1 + ksi]/ksi^(L + 1)
>
> devZ[L_] = Normal[Series[Z[L], {ksi, 0, 2}]]
> devZ[3]
>
> I get: devZ[3]= 1/4 -1/ksi^3+1/2 ksi +(ksi-ksi^2/2)/ksi^4.
> This code must yield:
> devZ[3]= ksi/5 - ksi^2/6 +0(ksi^3)
>
> How to correct this error.
>
> Any help will be very welcome.
>
> Lian.
>
>
>