Represent each of the following functions (a) by a Fourier cosine integral, (b) by a Fourier sine integral. Hint: See the discussion just before theParseval’s theorem.

Short Answer

Expert verified

By using the problem 15 and Fourier series cosine transform given function can be proved.

Step by step solution

01

Definition of Fourier series

The for Fourier series formula gives an expansion of a periodic function f (x) in terms of an horizonless sum of sines and cosines. It's used to putrefy any periodic function or periodic signal into the sum of a group of straightforward oscillating functions, videlicet sines and cosines.

02

Step 2:Given parameters

The given functions are

01cosαα2dα=π2

There need to prove the given functions using problem 15.

03

Use problem 15

The problem 15 says that

f(x)=4π01cos(αx)α2cos(αx)dα=2(ax),x[0,a]2(x+a),x[a,0]

04

Set the values of and  used in problem

Set the values that is a=1and x=0This gives:

f(0)=2=4π01cosαα2dαπ2=01cosαα2dα

Thus, using x=0and a=1in the problem 15 the given functions are proved.

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Most popular questions from this chapter

The functions in Problems 1 to 3 are neither even nor odd. Write each of them as the sum of an even function and an odd function.

(a) In|1-x| (b) (1+x)(sinx+cosx)

(a) Find the exponential Fourier transform off(x)=e|x|and write the inverse transform. You should find

0cosαxα2+1dα=π2e|x|

(b) Obtain the result in (a) by using the Fourier cosine transform equations (12.15).

(c) Find the Fourier cosine transform of f(x)=11+x2. Hint: Write your result in (b) with xandαinterchanged.

Find the average value of the function on the given interval. Use equation (4.8) if it applies. If an average value is zero, you may be able to decide this from a quick sketch which shows you that the areas above and below the xaxis are the same.

cosxon(0,3π)

Given f(x)={x,0<x<1-2,1<x<2

a) Sketch at least three periods of the graph of the function represented by the sine series for f(x). Without finding any series, answer thefollowing question:

b) To what value does the sine series in (a) converge at x=1? At x=2? At x=0? At x=-1?

c)If the given function is continued with the period 2and then is represented by a complex exponential series n=-Cneinπx, what is the value of n=|cn|2?

Starting with the symmetrized integrals as in Problem 34, make the substitutions α=2πph(where pis the new variable, his a constant), f(x)=ψ(x), localid="1664270725133" g(α)=h2πϕ(p); show that then

ψ(x)=1hϕ(p)e2πipxhdpϕ(p)=1hψ(x)e2πipxhdx|ψ(x)|2dx=|ϕ(p)|2dp

This notation is often used in quantum mechanics.

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