Fourier series expansion of Sin(x)

In summary, the conversation discusses the formula for the Fourier expansion of a general function f(x), which includes terms for a_0, a_n, and b_n. There is a discrepancy in the values of these terms, with HallsOfIvy pointing out that they should be 1/pi for a_n and b_n, and 1/2pi for a_0. The conversation also mentions the definite integrals needed to calculate the coefficients, with a mistake being made in the integration boundaries. Some members suggest checking for errors and splitting the thread for further discussion.
  • #1
therimalaya
7
0
May be simple, but I'm getting problem with doing Fourier series expansion of Sin(x) for -pi[tex]\leq[/tex]x[tex]\leq[/tex]pi
 
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  • #2


What does the formula for the Fourier expansion of a general function f(x) look like?
 
  • #3


CompuChip said:
What does the formula for the Fourier expansion of a general function f(x) look like?

f(x)=ao+[tex]\sum[/tex](ancos(nx)+bnsin(nx))

where,
ao=[tex]\frac{1}{\pi}[/tex][tex]\int[/tex]f(x) dx
an=[tex]\frac{1}{2\pi}[/tex][tex]\int[/tex]f(x)cos(nx) dx
bn=[tex]\frac{1}{2\pi}[/tex][tex]\int[/tex]f(x)sin(nx) dx
 
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  • #4


Isn't it supposed to be 1/pi for both a_n and b_n and 1/2pi for a_0? And in the formulae for a_n, b_n, these are supposed to be definite integrals not indefinite ones.
 
Last edited:
  • #5


Anyway, for the sine you can either calculate all these coefficients, but you can also just read off the values from the general expression.

HallsOfIvy, you may be right, didn't notice that. Asked the mods to look into it and maybe split the thread.
 
  • #6


Defennder said:
Isn't it supposed to be 1/pi for both a_n and b_n and 1/2pi for a_0? And in the formulae for a_n, b_n, these are supposed to be definite integrals not indefinite ones.

Yes there is definite intergral from -infinity to +infinity. I missed that.
Sorry

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  • #7


CompuChip said:
Anyway, for the sine you can either calculate all these
----------------

HallsOfIvy, you may be right, didn't notice that. Asked the mods to look into it and maybe split the thread.

I've tried that, May be I might have done some mistake, The integral term while calculating a_o, a_n and b_n vanishes and results zero. That is why I kept this in this forum. Any way I'll try that.
Thank You
 
  • #8
You mean they all vanished? Check again the ones for n = -1 and n = 1.
Also, check the integration boundaries. They are not [itex](-\infty, \infty)[/itex].
 

1. What is a Fourier series expansion of Sin(x)?

A Fourier series expansion of Sin(x) is a mathematical representation of a periodic function (in this case, Sin(x)) as a sum of sinusoidal functions with different frequencies and amplitudes. It is named after the mathematician Joseph Fourier who first introduced the concept in the 19th century.

2. How is a Fourier series expansion of Sin(x) calculated?

A Fourier series expansion of Sin(x) is calculated using the Fourier series formula, which involves integrating the function over one period and multiplying it by a series of trigonometric functions (e.g. sin(nx), cos(nx)) with varying coefficients. This process results in an infinite sum, which can be approximated by truncating the series to a finite number of terms.

3. What is the significance of a Fourier series expansion of Sin(x) in mathematics?

A Fourier series expansion of Sin(x) is significant because it allows us to represent a periodic function using a simpler and more compact form. It also has many applications in fields such as signal processing, differential equations, and quantum mechanics.

4. Can a Fourier series expansion of Sin(x) be used to approximate any periodic function?

Yes, a Fourier series expansion of Sin(x) can be used to approximate any periodic function with a finite number of terms. However, the accuracy of the approximation depends on the smoothness of the function and the number of terms used in the series.

5. Are there any real-world applications of Fourier series expansion of Sin(x)?

Yes, there are many real-world applications of Fourier series expansion of Sin(x). Some examples include audio signal processing, image compression, and power analysis in electrical engineering. It is also used in areas such as weather forecasting, medical imaging, and pattern recognition.

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