Fourier Series Transform Proof Help

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SUMMARY

The discussion focuses on the proof of the Fourier series, specifically the transition between the periodicity condition \( y(t+nT)=y(t) \) and the Fourier series representation \( y(t)=A_{0} + \Sigma^{\infty}_{n=1}[A_{n}cos(n\omega t) + B_{n}sin(n\omega t)] \). Participants clarify that the first equation indicates periodicity with period \( T \), while the second represents a Fourier series for functions periodic with period \( 2\pi/\omega \). The relationship \( \omega=2\pi/T \) is highlighted as a critical connection between the two equations, indicating that the discrete modes arise from the periodic nature of the function.

PREREQUISITES
  • Understanding of Fourier series and periodic functions
  • Familiarity with mathematical notation, particularly LaTeX
  • Knowledge of the relationship between frequency and period
  • Basic calculus, especially summation and integration concepts
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  • Study the derivation of Fourier series from periodic functions
  • Learn about the relationship between frequency and period in signal processing
  • Explore the use of LaTeX for mathematical expressions
  • Investigate the concept of Fourier transforms and their applications
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Students and professionals in mathematics, physics, and engineering who are working with Fourier series, signal analysis, or periodic functions will benefit from this discussion.

evotunedscc
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Can someone fill in the blank between these two steps? I can't find Fourier series proof anywhere and my professor just left it out.

(1) y(t+nT)=y(t)

(2) y(t)=A_{0} + \Sigma^{\infty}_{n=1}[A_{n}cos(n\omegat) + B_{n}sin(n\omegat)]

(The omega is going crazy on me... it's not supposed to be superscripted, just multiplied by n and t)
 
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evotunedscc said:
Can someone fill in the blank between these two steps? I can't find Fourier series proof anywhere and my professor just left it out.

(1) y(t+nT)=y(t)

(2) y(t)=A_{0} + \Sigma^{\infty}_{n=1}[A_{n}cos(n\omegat) + B_{n}sin(n\omegat)]

(The omega is going crazy on me... it's not supposed to be superscripted, just multiplied by n and t)

What do you mean by "steps between them"? The first just says y is periodic with period T and the second is the general expression of a Fourier series of a function periodic with period 2\pi/\omega- there is no mention of "T".

As for the LaTex, I would recommend putting the entire thing in [ t e x] not just individual parts:

y(t)=A_{0}+ \Sigma^{\infty}_{n=1}[A_{n}cos(n\omega t) + B_{n}sin(n\omega t)]

It looks better and is easier to type!
 
I would say that a general "Fourier expansion" is actually an integral. What (1) implies is that the modes are discrete and thus the integral becomes a sum, and therefore \omega=2 \pi/T, as Halls mentioned. Maybe this is the missing step you mean?
 
Last edited:
have u find the gap between those two statements[evotunedscc]?
 

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