Fourier transform - what integral limits

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Homework Help Overview

The discussion revolves around finding the Fourier transform of the unit rectangular distribution, specifically addressing the appropriate limits of integration for the transform given the function's definition.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants explore the limits of integration for the Fourier transform, questioning whether to include the boundaries of the interval or to use limits approaching those boundaries. There is also a discussion about the nature of the function and its behavior at the boundaries.

Discussion Status

Some participants have provided guidance on the limits of integration, suggesting that it may not matter whether the boundaries are included or approached as limits. The conversation reflects a mix of interpretations regarding the treatment of the boundaries in the context of the Fourier transform.

Contextual Notes

There is a mention of the uniqueness of Fourier transforms and how functions differing on a set of measure zero may still have the same transform, which could influence the discussion on the limits.

zezima1
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Find the Fourier transform of the unit rectangular distribution f(t) = 1 for ltl<1 else 0
Since e-iωt is zero except for t in ]-1;1[ it must be an integral over this interval. But should I take the boundaries as -1 and 1? Because they are not included in the interval where e-iωt is not zero but rather supremum and infimum for it. Would it better to put the limits lim t->1 and lim t->-1?
 
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What?
The exponent never vanishes for finite values.
 
umm the Fourier transform is:

-∞f(t)e-iωtdt

But since f(t)=0 for t≥1, t≤-1 you integrate from -1 to 1?
 
zezima1 said:
umm the Fourier transform is:

-∞f(t)e-iωtdt

But since f(t)=0 for t≥1, t≤-1 you integrate from -1 to 1?

Yes.
 
zezima1 said:
Find the Fourier transform of the unit rectangular distribution f(t) = 1 for ltl<1 else 0
Since e-iωt is zero except for t in ]-1;1[ it must be an integral over this interval. But should I take the boundaries as -1 and 1? Because they are not included in the interval where e-iωt is not zero but rather supremum and infimum for it. Would it better to put the limits lim t->1 and lim t->-1?
I think you meant f(t) where you wrote e-iωt.

Regarding your question about the limits, it turns out it doesn't matter. You can look up some statement about the uniqueness of Fourier transforms. I think it's something like two functions have the same Fourier transform if they differ over a set of points of measure 0.
 

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