Power series method of solving ODE

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Discussion Overview

The discussion revolves around solving the ordinary differential equation (ODE) given by y" + y' + sin^2(x)y - 2sinx = 0 using the power series method. Participants explore different approaches to derive a recurrence formula for the series solution.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant requests assistance with deriving a recurrence formula using the power series method and the Maclaurin series for sin(x).
  • Another participant suggests substituting sin^2(x) with (1 - cos(2x))/2 and expanding the series again as a potential approach.
  • A third participant expresses appreciation for the suggestion to use the substitution.
  • A different participant indicates difficulty with the substitution and insists on using the Maclaurin series to express sin^2 in terms of x.
  • Another participant questions the need for expressing sin^2 in terms of x, arguing that it is inherently in terms of x and emphasizes that using the Maclaurin series for cos(2x) may be easier than for sin^2(x).

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to take, with differing opinions on the use of the Maclaurin series and the substitution for sin^2(x). The discussion remains unresolved regarding the most effective method to derive the recurrence formula.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the series expansions and the specific forms of the functions involved. The effectiveness of the proposed substitutions and series expansions is not fully explored.

femi
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Please can somebody help me with this problem

y" + y' + sin^2(x)y - 2sinx = 0

I used power series method and i used the macclurin expresion for sinx but i was not able to get a recurrence formula.
 
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I did not check it but did you try plugging in

[itex]\sin^2(x) = \frac{1-\cos(2x)}{2}[/itex]

and expand your series again?
 
Very nice suggestion.
 
I cann't get it that way. I think i need to use the macclurin series so that sin^2 will be in terms of x. Pls any other suggestion?
 
I have no idea what you mean by "i need to use the macclurin series so that sin^2 will be in terms of x". Of course [itex]sin^2 x[/itex] is in terms of x- that has nothing to do with a series! And trambolin did not mean that you shouldn't use MacLaurin series but that it is far easier to write a MacLaurin series for cos(2x) than to have a MacLaurin series, for sin(x) squared!
 

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