How to get the real and imaginary parts of a power series?

*To*: mathgroup at smc.vnet.net*Subject*: [mg79998] How to get the real and imaginary parts of a power series?*From*: Gordon Smith <gsmithsf at hotmail.com>*Date*: Fri, 10 Aug 2007 01:52:48 -0400 (EDT)

Suppose s = Series[Cosh[(x + I y)u, {u,0,2}]. How can I get the real part 1 + 1/2(x^2 - y^2) u^2 + O(u^3) and the imaginary part x y u^2 + O(u^3) ? I thought ComplexExpand[Re[s]] should give me the real part of s, but it just gives me s unchanged. (Mathematica newbie here!)

**Follow-Ups**:**Re: How to get the real and imaginary parts of a power***From:*Murray Eisenberg <murray@math.umass.edu>

**RE: How to get the real and imaginary parts of a power series?***From:*"Jaccard Florian" <Florian.Jaccard@he-arc.ch>