Fourier Series - Half Range Expansions

In summary: Once we have all of the coefficients, we can then plug them into the formula for the Fourier series expansion: f(x) = a0/2 + ∑ [an*cos(nπx/p) + bn*sin(nπx/p)]. This will give us the half range expansion of the given function. In summary, to find the half range expansion of the given function, we can divide it into its odd and even parts and use the formula for the Fourier series expansion to find the coefficients a0, an, and bn. Once we have all of the coefficients, we can then plug them into the formula
  • #1
erok81
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1. Homework Statement [/b]

Find the half range expansion of the given function.

I tried to show f(x) using LaTeX but couldn't figure out how to stack three rows, so I have attached an image instead.

Homework Equations



Fourier series expansions for a0, an, bn - I can post these once I get to this point.

The Attempt at a Solution



In my image you can see how I've tried to graph this in order to get my even and odd functions. I know this isn't correct, but cannot figure out how to do it. The p throws me off, I know it is usually for the period but I can't figure out how that plays into this case. There aren't any examples in my text that are close to this.

Any tips on even how to get my graph started would be appreciated. Then we can go from there extending them odd/even over a period.
 

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  • #2
2. Homework StatementFind the half range expansion of the given function.f(x) = x^3 - 4x^2 + px + 2, -p/2 < x < p/2Homework EquationsFourier series expansions for a0, an, bnThe Attempt at a SolutionTo find the Fourier series expansion, we can first divide the function into its odd and even parts. The even part is given by the equation f_e(x) = x^3 - 4x^2, and the odd part is given by the equation f_o(x) = px + 2.Next, we can use the formula for the Fourier series expansion to find the coefficients a0, an, and bn. For the even part, the coefficient a0 is given by the equation a0 = (2/p)∫f_e(x) dx from -p/2 to p/2. This gives us a0 = (2/p) [(x^4/4) - (2x^3/3) + (4x^2/2)] evaluated from -p/2 to p/2. Using the fundamental theorem of calculus, we can simplify this to a0 = (2/p)[p^4/8 - p^3/4 + 2p^2/2]. Similarly, the coefficients an and bn for the even part can be found using the equations an = (2/p)∫f_e(x)cos(nπx/p) dx from -p/2 to p/2, and bn = (2/p)∫f_e(x)sin(nπx/p) dx from -p/2 to p/2. For the odd part, the coefficient a0 is 0 since the integral of an odd function from -p/2 to p/2 is 0. The coefficients an and bn for the odd part can be found using the equations an = (2/p)∫f_o(x)cos(nπx/p) dx from -p/2 to p/2, and bn = (2
 

1. What is a Fourier Series - Half Range Expansion?

A Fourier Series - Half Range Expansion is a mathematical representation of a periodic function using a combination of sine and cosine functions. It is used to approximate a function on a specific interval, typically from 0 to π, instead of the entire real line.

2. Why is a half range expansion used instead of a full range expansion?

A half range expansion is used because it simplifies the calculation of Fourier coefficients and allows for easier integration and manipulation of the series. It also eliminates the need for odd or even extensions of the function, which can be cumbersome and time-consuming.

3. How do I determine the coefficients of a Fourier Series - Half Range Expansion?

The coefficients of a Fourier Series - Half Range Expansion can be determined using the formula: an = (2/π) * ∫0π f(x) * cos(nx) dx and bn = (2/π) * ∫0π f(x) * sin(nx) dx. These integrals can be evaluated using techniques such as integration by parts or trigonometric substitutions.

4. What is the difference between a half range expansion and a full range expansion?

The main difference between a half range expansion and a full range expansion is the interval on which the Fourier Series is defined. A half range expansion is defined on the interval from 0 to π, while a full range expansion is defined on the entire real line. This difference affects the calculation of coefficients and the number of terms needed to accurately represent the function.

5. What are some applications of Fourier Series - Half Range Expansions?

Fourier Series - Half Range Expansions are commonly used in mathematics, physics, and engineering to approximate periodic functions, such as sound waves, electrical signals, and heat distribution. They are also used in signal processing, image compression, and data analysis.

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