What is the rules regarding convergence of a Fourier series?

In summary, the conversation discusses the rules for drawing out the full function of a Fourier series when given only part of a period. It is mentioned that at least one full period is needed for this to be possible. The choice between odd and even extension is also discussed, with the preference being the continuous function over one with a jump discontinuity. It is also noted that the smoother the function, the quicker the Fourier series converges. The type of convergence assumed is also brought up.
  • #1
zheng89120
149
0
If you are given part of a period of a Function, what rules would you apply to draw out the full function, so that it converges as quickly as possible as a Fourier series?

thanks
 
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  • #2
If you only know one part of the period, then there is no way to "draw out the full function." You need at least one full period for that.
 
  • #3
zheng89120 said:
If you are given part of a period of a Function, what rules would you apply to draw out the full function, so that it converges as quickly as possible as a Fourier series?

thanks

Your question is pretty vague. But if, for example, you have the function defined on (0,p) and you wish to choose between the odd and even extension to (-p,0) to use a half-range expansion, if one of those choices gives a continuous function and the other has a jump discontinuity, the continuous one would be preferred.

Generally, the smoother the function, the quicker the FS converges.
 
  • #4
What kind of convergence are we assuming L2[a,b], etc?
 

1. What is a Fourier series?

A Fourier series is a mathematical representation of a periodic function as a sum of sine and cosine functions with different amplitudes and frequencies.

2. What is the purpose of a Fourier series?

The purpose of a Fourier series is to approximate a periodic function with a simpler combination of trigonometric functions, making it easier to analyze and manipulate.

3. What are the rules for convergence of a Fourier series?

The rules for convergence of a Fourier series state that the series will converge to the original function if the function is continuous and piecewise smooth, and if the series satisfies certain conditions such as the Dirichlet conditions.

4. What are the Dirichlet conditions?

The Dirichlet conditions are a set of criteria that a function must satisfy in order for its Fourier series to converge. These conditions include the function being periodic, having a finite number of discontinuities, and having a finite number of extrema within a given interval.

5. Can a Fourier series converge to a non-periodic function?

No, a Fourier series can only converge to a periodic function. If a non-periodic function is to be approximated, it must first be made periodic by extending it periodically outside of its original domain.

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