       Re: Exclude O[] from Series[] for Solve[] in Mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg92845] Re: Exclude O[] from Series[] for Solve[] in Mathematica
• From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
• Date: Wed, 15 Oct 2008 05:36:03 -0400 (EDT)

```I expand a function as a Series[] but the O[] part prevents Solve[] from
working. I try Part[] and it returns something which also confuses
Solve[]. First[] works, but produces useless results, but this is why I am
sure this is what I want to do.

Hi, Vasos,
There is a function Normal[] that does the job. Compare:

In:= Series[Sin[x], {x, 0, 5}]

Out= (SeriesData[\$CellContext`x, 0, {
1, 0, Rational[-1, 6], 0, Rational[1, 120]}, 1, 6, 1])

with the following:

In:= Normal[Series[Sin[x], {x, 0, 5}]]

Out= x - x^3/6 + x^5/120

Check Help/Series for more details.

With this the Solve operator works:

In:= Solve[Normal[Series[Sin[x], {x, 0, 5}]] == 0, x]

Out= {{x -> 0}, {x -> -Sqrt[2 (5 - \[ImaginaryI] Sqrt)]}, {x ->
Sqrt[2 (5 - \[ImaginaryI] Sqrt)]}, {x -> -Sqrt[
2 (5 + \[ImaginaryI] Sqrt)]}, {x -> Sqrt[
2 (5 + \[ImaginaryI] Sqrt)]}}

Have success, Alexei

--
Alexei Boulbitch, Dr., Habil.
Senior Scientist

IEE S.A.
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