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Re: Series expansion question

  • To: mathgroup at
  • Subject: [mg122705] Re: Series expansion question
  • From: Bill Rowe <readnews at>
  • Date: Mon, 7 Nov 2011 05:51:29 -0500 (EST)
  • Delivered-to:

On 11/6/11 at 5:56 AM, recif at (Recif) wrote:

>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

>However when I assign values to a and b:
>a = x0 + z
>b = y0 + z

>gts[a,b] gives me an error

How about:

In[2]:= gts[x_, y_] :=
  Block[{a, b},
   Normal[Series[g[a, b], {a, x0, 1}, {b, y0, 1}]] /. {a -> x, b
-> y}]

In[3]:= gts[x + x0, y + y0]

Out[3]= y*(x*Derivative[1, 1][g][x0, y0] +
     Derivative[0, 1][g][x0, y0]) +
    x*Derivative[1, 0][g][x0, y0] + g[x0, y0]

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