Finding particular solution with fourier series

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SUMMARY

The discussion focuses on solving the differential equation x'' + ω²x = cos²(t) sin²(t) and determining the values of ω for which it has a solution with a period of 2π. The key challenge identified is finding the Fourier series representation of the right-hand side, which leads to confusion as the coefficients An and Bn are calculated to be zero. It is concluded that the right-hand side is already in the form of a Fourier series, simplifying the analysis.

PREREQUISITES
  • Understanding of differential equations, specifically second-order linear differential equations.
  • Familiarity with Fourier series and their applications in solving periodic functions.
  • Knowledge of trigonometric identities, particularly the product-to-sum formulas.
  • Basic skills in mathematical analysis and periodic function behavior.
NEXT STEPS
  • Study the derivation and application of Fourier series in solving differential equations.
  • Explore trigonometric identities to simplify expressions like cos²(t) sin²(t).
  • Learn about the conditions for periodic solutions in second-order differential equations.
  • Investigate the implications of ω values on the stability and periodicity of solutions.
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Mathematicians, physics students, and engineers interested in differential equations and Fourier analysis, particularly those working on periodic systems and wave phenomena.

naggy
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I was wondering what to do if I have a DE like this

[tex]x'' + \omega^2x = \cos^2(t) \sin^2(t)[/tex]

I have to decide for what omega it has a solution with period 2pi.

Now to solve this I have to find the Fourier series representation of the right hand side, but the problem is that I get all An = Bn = 0 ??
 
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wait! The right hand side already is a Fourier series
 

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