Can someone explain this?(Taylor polynomials)

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    Explain Polynomials
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Discussion Overview

The discussion revolves around the calculation of Taylor polynomials for the function f(x)=1/(1+x^2) at the point a=0, specifically focusing on the 2nd and 4th degree polynomials. Participants are examining the nature of the solutions provided and whether they meet the criteria for polynomials.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant presents the Taylor polynomials for the 2nd and 4th degree as P2 = 1-x^2 and P4 = 1-x^2+x^4.
  • The same participant claims to have derived different expressions for the 2nd and 4th degree, specifically -2x/[(1+x^2)^2] and 12x/[(1+x^2)^4], respectively.
  • Another participant questions the polynomial nature of the solutions provided, suggesting that they do not conform to the definition of polynomials.
  • A further reply references a source that outlines the requirements for terms in a polynomial, emphasizing that they must consist of coefficients multiplied by x raised to positive integer powers.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the nature of the solutions presented, with some arguing that the solutions are not polynomials while others assert their validity.

Contextual Notes

There is a lack of clarity regarding the definitions being used for polynomials, as well as the assumptions underlying the calculations of the Taylor polynomials.

NINHARDCOREFAN
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For function f(x)=1/(1+x^2), calculate Taylor polynomials for the 2nd and 4th degree about the point a=0.

The answer was:

P2 = 1-x^2;
P4 = 1-x^2+x.^4

for 2nd degree I got -2x/[(1+x^2)^2]
for 4th degree I got 12x/[(1+x^2)^4]
 
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But neither of your solutions are polynomials?
 
Why aren't they?
 
Last edited:

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