What is the trick to simplifying the Taylor series of 1/(1 + x^2)?

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Discussion Overview

The discussion revolves around the simplification of the Taylor series for the function 1/(1 + x^2), specifically centered around x = 0. Participants explore various methods for deriving the series and seek clever techniques to simplify the process.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant expresses difficulty in simplifying the Taylor series and questions if there is a clever trick to achieve the desired form.
  • Another participant suggests calculating a few derivatives at x = 0 to identify a pattern, proposing that the nth derivative at this point could be 0 for odd n and (-1)^n n! for even n.
  • A similar response reiterates the approach of finding a pattern in the derivatives and confirms the central point is x = 0.
  • Another participant proposes rewriting the function as 1/(1 + x^2) = 1/(1 - (-x^2)) to expand it using a geometric series or applying the Leibniz product rule, noting that the third derivative of (1 + x^2) is zero.

Areas of Agreement / Disagreement

Participants present multiple approaches to the problem, indicating that there is no consensus on a single method for simplifying the Taylor series. Various techniques are suggested, and the discussion remains open-ended.

Contextual Notes

Some participants mention the need to calculate derivatives and identify patterns, but the discussion does not resolve the effectiveness of the proposed methods or the correctness of the derivatives calculated.

animboy
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The equation starts at B and this is my attempt. As you can see it soon complicates and doesn't look like what t should since I already know what the Taylor series of his function should look like. Is there some clever trick to it that I am missing? PS the series is centred around x = 0.

[PLAIN]http://img823.imageshack.us/img823/3459/phys.png
 
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A Taylor's series about what central point? Rather than work out a large number of derivatives, I would calculate a few derivatives at the given point and try to find a pattern.

For example, the Taylor's series about x= 0 (the McLaurin series), has f(0)= 1, f'(0)= 0, f''(0)= -2, f'''(0)= 0, f''''(0)= 4!, etc. so I would hypothesize that the nth derivative, at 0, is 0 for odd n, [itex](-1)^n n![/itex] for n odd. Then I would try to prove that is true by induction.
 
HallsofIvy said:
A Taylor's series about what central point? Rather than work out a large number of derivatives, I would calculate a few derivatives at the given point and try to find a pattern.

For example, the Taylor's series about x= 0 (the McLaurin series), has f(0)= 1, f'(0)= 0, f''(0)= -2, f'''(0)= 0, f''''(0)= 4!, etc. so I would hypothesize that the nth derivative, at 0, is 0 for odd n, [itex](-1)^n n![/itex] for n odd. Then I would try to prove that is true by induction.

it's at x = 0, I will try your method and post a pic.
 
Either write
1/(1+x^2)=1/(1-(-x^2))
and expand in geometric series
or apply Leibniz product rule to
[(1+x^2)/(1+x^2)]
and note
(1+x^2)'''=0
 

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