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Re: Series expansion question

  • To: mathgroup at
  • Subject: [mg122717] Re: Series expansion question
  • From: Alexei Boulbitch <Alexei.Boulbitch at>
  • Date: Mon, 7 Nov 2011 05:53:38 -0500 (EST)
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Hi, Recif,



gts[x_, y_] := Normal[Series[g[x, y], {x, x0, 1}, {y, y0, 1}]];

gts[x, y] /. {x -> x0 + z, y -> y0 + z}

may help. Try. Have fun.

I defined a function:

gts[x_, y_] := Normal[Series[g[x, y], {x, x0, 1}, {y, y0, 1}]]

and when I use it with 'a' and 'b' undefined, I get the value I expect:

gts[a, b]

g[x0,y0] + (a-x0) g^(1,0)[x0,y0] + (b-y0) g^(0,1)[x0,y0] ...

However when I assign values to a and b:

a = x0 + z

b = y0 + z


gives me an error:

General::ivar: "x0+z is not a valid variable"


I would appreciate any help to fix this.



Alexei BOULBITCH, Dr., habil.


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