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1. Find the Fourier series of the given function f (x), which is assumed to have the period

2π. Show the details of your work.
() = { , − < < 0
− , 0 < <

1. Find the Fourier series of the given function f (x), which is assumed to have the-example-1
User Giovanni B
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1 Answer

5 votes

Answer:

The given function f(x) is:

f(x) = { 1, -π < x < 0

{ -1, 0 < x < π

Since the function is odd and has period 2π, the Fourier series will only have sine terms. The Fourier series of f(x) can be written as:

f(x) = Σ[b_n sin(n x)], where n >= 1

where b_n is the n-th Fourier coefficient, given by:

b_n = (1/π) ∫[0,π] f(x) sin(n x) dx

We can evaluate the integral to find the Fourier coefficients:

b_n = (1/π) ∫[0,π] f(x) sin(n x) dx

= (1/π) [ ∫[0,π/2] sin(n x) dx - ∫[π/2,π] sin(n x) dx ]

= (1/π) [ -cos(n x)/n |[0,π/2] + cos(n x)/n |[π/2,π] ]

= (1/π) [ (-cos(n π/2)/n + 1/n) - (cos(n π) - cos(n π/2))/n ]

= (1/π) [ (1 - (-1)^n) / n ]

Therefore, the Fourier series of f(x) is:

f(x) = Σ[(1 - (-1)^n)/(n π) sin(n x)]

Where the sum is taken over all odd integers n.

User Samir Aleido
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