Finding the Fourier Series of a Cosine Function.

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SUMMARY

The discussion centers on finding the Fourier series for the function f(x) = Acos(∏x/L). The Fourier series is derived using the formulas for a0 and an, where a0 = 0 and an is calculated using the integral an = 2/L ∫ f(x)cos(n∏x/L) dx. Participants clarify that the function has a period of 2L, necessitating the use of the correct Fourier series expansion that includes both cosine and sine terms. The conversation also highlights the importance of understanding the periodicity of the function and the implications of using different bounds in the integrals.

PREREQUISITES
  • Understanding of Fourier series and their components (a0, an, bn).
  • Knowledge of integration techniques, particularly for trigonometric functions.
  • Familiarity with the concept of periodic functions and their properties.
  • Ability to interpret mathematical notation and LaTeX formatting.
NEXT STEPS
  • Study the derivation of Fourier series for periodic functions with different periods.
  • Learn about the use of trigonometric identities in simplifying integrals involving cosine functions.
  • Explore the implications of function periodicity on Fourier series representation.
  • Investigate the relationship between different notations for period (L vs D) in Fourier analysis.
USEFUL FOR

Students studying Fourier analysis, mathematicians working with periodic functions, and educators seeking to clarify Fourier series concepts in a classroom setting.

  • #31
Uart,
The question is posted in bold a few posts back and that is exactly how it appears on the piece of paper I have So yeah there's as lot of assuming it seems
 
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  • #32
I don't think there is much left to be said about this problem. Yes, the statement of the problem leaves lots go be desired. However, given the way it was stated, the natural assumption is that L is a half period, which is the usual notation. And the point of the problem is for the student to learn a couple of things.

1. The function itself is its own finite Fourier Series.
2. That if you calculate the Fourier Coefficients you need to be careful about using identities (in this case because of the situation when n=1).
 
  • #33
Agreed. I'd just like to thank you all for your input though, much appreciated! (:
 
  • #34
ProPatto16 said:
Uart,
The question is posted in bold a few posts back and that is exactly how it appears on the piece of paper I have So yeah there's as lot of assuming it seems

Ok I see it now, thanks.
Given the function f(x) = Acos(∏x/L), determine its Fourier series.

there is nothing else, no domain specified or anything.

That's just a poorly written question. Take the period as whatever you want in that case, using 2L is definitely the easiest. :smile:
 

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