Prove FT^2(f(x))=f(-x): Answers & Tips

In summary, FT^2 stands for Fourier Transform squared and is used to analyze and manipulate signals and images in various fields of science. The equation FT^2(f(x))=f(-x) is true for any function f(x) that satisfies the conditions for Fourier transform, and can be proven using the property of symmetry. An example using the function f(x) = sin(x) is provided to explain this equation. Some applications of this equation in science include signal processing, image processing, quantum mechanics, and optics.
  • #1
liorda
28
0
Prove: [tex]FT^2(f(x))=f(-x)[/tex] where [tex]FT[/tex] is the Fourier transform.

I tried to change [tex]x[/tex] into [tex]-x'[/tex] but with no success.

Do I need to separate cases for even f and odd f?
 
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  • #2
You just need to realize that e.g., integral(exp(i*k*t1)*exp(i*k*t2)*dk) is proportional to delta(t1+t2).
 

1. What is the full form of FT^2?

The full form of FT^2 is Fourier Transform squared.

2. How do you prove FT^2(f(x))=f(-x)?

To prove FT^2(f(x))=f(-x), you can use the property of symmetry of Fourier transform, which states that the Fourier transform of a function is symmetric about the origin. Therefore, FT(f(-x))=FT(f(x)), and by squaring both sides, we get FT^2(f(x))=FT^2(f(-x)).

3. Is the given equation always true for any function f(x)?

Yes, the equation FT^2(f(x))=f(-x) is true for any function f(x) that satisfies the conditions for Fourier transform. However, it is important to note that the function must be square-integrable for the Fourier transform to exist.

4. Can you provide an example to explain this equation?

Sure, consider the function f(x) = sin(x). The Fourier transform of this function is F(k) = πδ(k-1) - πδ(k+1), where δ is the Dirac delta function. Now, applying the property of symmetry, we get FT(f(-x)) = F(-k) = πδ(-k-1) - πδ(-k+1). Squaring both sides, we get FT^2(f(x)) = F^2(k) = π^2δ(k-1)^2 + π^2δ(k+1)^2 - 2π^2δ(k-1)δ(k+1). Simplifying this, we get FT^2(f(x)) = π^2 + π^2 - 2π^2 = π^2 = f(-x), which proves the given equation.

5. What are some applications of this equation in science?

The equation FT^2(f(x))=f(-x) has many applications in various fields of science, including signal processing, image processing, quantum mechanics, and optics. It is used to analyze and manipulate signals and images, as well as to solve differential equations in physics and engineering. It also plays a crucial role in understanding the behavior of waves and particles in quantum mechanics and optics.

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