How's Fourier series modified for function f(t)= f(2Pi t)?

In summary, the coefficients of the Fourier series for a function with a period 2πT are modified by using the new limits of integration [-T,T] for the integrals and by dividing by the period 2πT. The coefficients are also expressed in terms of the new variable t and its corresponding sine and cosine functions.
  • #1
Poirot
94
2

Homework Statement


How are the coefficients of the Fourier series modified for a function with a period 2πT?

Homework Equations


a0 = 1/π ∫π f(x) dx
an = 1/π ∫π f(x) cos(nx) dx
bn = 1/π ∫π f(x) sin(nx) dx

The Attempt at a Solution


I tried letting x= t/T
so dx = dt/T and the limits x = ± π, x = ± πT
and I was going to plug this into the integrals but I don't think it's right.

Any help would be greatly appreciated, thanks!
 
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  • #2
Usually the function f(t) is periodic over period T. (not ## 2 \pi ## T). The integration over t will go from t=0 to t=T. You can readily google the topic to get the precise form of the coefficients, etc.
 
  • #3
For general period ##2p## the Fourier coefficients are$$
b_n = \frac 1 p \int_{-p}^p f(x) \sin(\frac{n\pi x}{p})~dx $$ $$
a_n =\frac 1 p \int_{-p}^p f(x) \cos(\frac{n\pi x}{p})~dx $$ $$
a_0 = \frac 1 {2p}\int_{-p}^p f(x)~dx$$
##a_0## may or may not have the ##2## in the denominator depending on whether you start the FS with ##a_0## or ##\frac {a_0} 2##.
 

1. How is the Fourier series modified for a function with a period of 2π?

The main modification for a function with a period of 2π is that the coefficients in the Fourier series will be multiplied by a factor of 2π. This is because the period of the function is now 2π instead of the usual 2π/L, where L is the period of the function.

2. Can a function with a period of 2π be expressed using a Fourier series?

Yes, a function with a period of 2π can be expressed using a Fourier series. The coefficients will just be modified as mentioned before, and the series will still converge to the function as the number of terms approaches infinity.

3. How do the Fourier coefficients change for a function with a period of 2π?

The Fourier coefficients for a function with a period of 2π will be multiplied by a factor of 2π, as mentioned before. This means that the amplitudes of the harmonics in the Fourier series will be larger compared to a function with a smaller period.

4. Are there any other modifications to the Fourier series for a function with a period of 2π?

Apart from the multiplication of the coefficients by 2π, there are no other modifications to the Fourier series for a function with a period of 2π. The general formula for calculating the coefficients remains the same, and the series will still have the same properties such as convergence and periodicity.

5. Why is it important to modify the Fourier series for a function with a period of 2π?

The modification of the Fourier series for a function with a period of 2π is important because it ensures that the series accurately represents the function. If the coefficients are not modified, the series will not converge to the function as the number of terms increases. Additionally, the modified coefficients also reflect the change in the period of the function, making the series more accurate for this specific type of function.

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