Beginner--Error in Series expansion
- To: mathgroup at smc.vnet.net
- Subject: [mg68155] Beginner--Error in Series expansion
- From: abdou.oumaima at hotmail.com
- Date: Wed, 26 Jul 2006 02:26:19 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
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.