Fourier Series of x/3: Finding Coefficients and Solutions

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SUMMARY

The discussion focuses on finding the Fourier series coefficients for the function x/3 over the interval [0, 2π]. The user initially miscalculated the coefficients, assuming that a0 and ak are zero due to the odd function property. However, they later recognized the need to adjust their approach for the specified period. The correct formula for the coefficients bk is given as bk = (1/L) ∫ from 0 to L f(x) sin(kπx/L) dx, with L defined as 2π in this context.

PREREQUISITES
  • Understanding of Fourier series and their coefficients
  • Knowledge of integration techniques, particularly integration by parts
  • Familiarity with periodic functions and their properties
  • Basic knowledge of trigonometric functions and their integrals
NEXT STEPS
  • Study the derivation of Fourier series coefficients for piecewise functions
  • Learn about the properties of odd and even functions in Fourier analysis
  • Explore integration by parts in the context of Fourier series
  • Review the implications of changing the period in Fourier series calculations
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Students studying mathematical analysis, particularly those focusing on Fourier series, as well as educators and professionals looking to deepen their understanding of periodic functions and their representations.

Kuma
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Homework Statement



I'm trying to find the Fourier series of x/3.


Homework Equations





The Attempt at a Solution



So i believe that it is an odd function so a0, ak = 0. To find bk:

bk = 1/3pi int (x sin kx dx) from -pi to pi. From integration by parts
= 1/3pi ([x sin kx from -pi to pi]+ 1/k int (cos kx dx) from -pi to pi)
= 1/3pi [(pi sin k pi + pi sin -k pi) +1/k^2 (sin k pi - sin -k pi)]
I think that works out to be 0? Is that right?
 
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Well, by inspection [itex]b_k[/itex] cannot all be zero, because then the whole function would be zero.
 
Sorry I made a big mistake. Forgot to mention the period which is from 0 to 2pi. Also my integration by parts was wrong which resulted in bk being 0 when it shouldn't be.

First question, how do i do it with a period from 0 to 2pi. Is my integrand just from 0 to 2pi?
The formula for bk is 1/L*integral from L to -L f(x) sin k pi x/L dx

What is L in this case? 2pi??
 

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