Re: Simlifying series expansion

*To*: mathgroup at smc.vnet.net*Subject*: [mg20581] Re: [mg20550] Simlifying series expansion*From*: BobHanlon at aol.com*Date*: Sat, 30 Oct 1999 14:54:55 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Peter, You are looking for the Series with x^g factored out, i.e., n = 5; s = x^g * Series[Sin[x], {x, 0, n}]; Redefine Series to automatically handle the factoring mySeries[expr_, {x_Symbol, x0_?NumericQ, n_Integer}] := Module[{t = Series[#, {x, x0, n}] & /@ expr, f}, f = Times @@ Cases[t, y_?(! FreeQ[#, Series] &) :> First[y]]; f * Series[expr/f, {x, x0, n}]] s == mySeries[x^g Sin[x], {x, 0, n}] True I haven't tested this very thoroughly so there may be situations where it does not work as expected. Bob Hanlon In a message dated 10/30/1999 4:07:15 AM, pollner at physik.uni-marburg.de writes: >I am interested to calculate power series like > >x^g Sin[x] = x^(g+1) + o[x^(g+3)] > >How to do it with Mathematica? The naive > >Series[x^g Sin[x],{x,0,IntegerPart[g+4]}] > >do not work. >