What is the Fourier Transform of sin?

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SUMMARY

The Fourier transform of the function f(t) = sin(t) for the interval -π < t < π is correctly computed by integrating from -π to π, as the function is zero outside this range. The initial confusion arose from the standard Fourier transform limits of -∞ to ∞, which include the Dirac delta function. However, since the function is defined to be zero outside the specified interval, the integration limits can be adjusted accordingly. This approach eliminates the need for the Dirac delta function in this specific case.

PREREQUISITES
  • Understanding of Fourier transforms and their properties
  • Familiarity with the Dirac delta function
  • Knowledge of piecewise functions
  • Basic calculus skills for integration
NEXT STEPS
  • Study the properties of the Fourier transform, particularly for piecewise functions
  • Learn about the Dirac delta function and its applications in Fourier analysis
  • Explore the implications of changing integration limits in Fourier transforms
  • Practice computing Fourier transforms of other trigonometric functions
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Students in mathematics or engineering, particularly those studying signal processing or Fourier analysis, will benefit from this discussion.

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Homework Statement



Hey guys.
I need to find the Fourier transform of sin, is this right?

http://img156.imageshack.us/img156/5531/scan0004r.jpg

I searched the internet but all I could find is the answer with the dirac delta and I don't need that.

Thanks.


Homework Equations





The Attempt at a Solution

 
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The Fourier transform of sin(t) involves the Dirac delta function. What do you mean by "I don't need that"? And why did you change the limits from -∞ to ∞ to -π to π in your integral?
 
dx said:
The Fourier transform of sin(t) involves the Dirac delta function. What do you mean by "I don't need that"? And why did you change the limits from -∞ to ∞ to -π to π in your integral?

Oh, sorry, I need to find it from -pi to pi.
Is there something wrong with what I did?

Thanks.
 
I didn't read your whole solution, but there is a mistake in your first step. The Fourier transform integral goes from -∞ to ∞. Why did you change those limits?
 
dx said:
I didn't read your whole solution, but there is a mistake in your first step. The Fourier transform integral goes from -∞ to ∞. Why did you change those limits?

Yeah, I need to find it from -pi to pi.
Is that way it doesn't involves Dirac function?

Thanks.
 
No! It's not from -pi to pi. It's -∞ to ∞.
 
dx said:
No! It's not from -pi to pi. It's -∞ to ∞.

:smile:

But that is the question.
Find Fourier transform of sin in -pi<t<pi.

What do you mean?

Thanks.
 
Your question is to transform the function f(t) = \left\{ \begin{matrix} \sin t &amp; \mathrm{if}\; -\pi &lt; t &lt; \pi \\ 0 &amp; \mathrm{otherwise} \end{matrix} \right ?
 
Cyosis said:
Your question is to transform the function f(t) = \left\{ \begin{matrix} \sin t &amp; \mathrm{if} -\pi &lt; t &lt; \pi \\ 0 &amp; \mathrm{otherwise} \end{matrix} \right ?

Yeah, sorry for the misconfusion.
 
  • #10
Then your approach is correct since the function is zero outside -pi<t<pi anyway so you may as well integrate from -pi to pi.
 
  • #11
Ah, now it makes sense! Thanks Cyosis!
 
  • #12
You're welcome.
 

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