Math Problem Statement

Find the Fourier cosine transform of e^-2x^2

Solution

The Fourier cosine transform Fc{f(x)}\mathcal{F}_c\{f(x)\} of a function f(x)f(x) is defined as:

Fc{f(x)}=0f(x)cos(kx)dx\mathcal{F}_c\{f(x)\} = \int_{0}^{\infty} f(x) \cos(kx) \, dx

For the function f(x)=e2x2f(x) = e^{-2x^2}, the Fourier cosine transform is:

Fc{e2x2}=0e2x2cos(kx)dx\mathcal{F}_c\{e^{-2x^2}\} = \int_{0}^{\infty} e^{-2x^2} \cos(kx) \, dx

This integral can be evaluated using a known result:

0eax2cos(bx)dx=12πaeb24a\int_{0}^{\infty} e^{-ax^2} \cos(bx) \, dx = \frac{1}{2} \sqrt{\frac{\pi}{a}} e^{-\frac{b^2}{4a}}

In our case, a=2a = 2 and b=kb = k, so the Fourier cosine transform becomes:

Fc{e2x2}=12π2ek28\mathcal{F}_c\{e^{-2x^2}\} = \frac{1}{2} \sqrt{\frac{\pi}{2}} e^{-\frac{k^2}{8}}

Thus, the Fourier cosine transform of e2x2e^{-2x^2} is:

Fc{e2x2}=π22ek28\mathcal{F}_c\{e^{-2x^2}\} = \frac{\sqrt{\pi}}{2\sqrt{2}} e^{-\frac{k^2}{8}}

Would you like more details on any part of this process?


Here are some related questions:

  1. What is the significance of the Fourier cosine transform in signal processing?
  2. How does the Fourier sine transform differ from the cosine transform?
  3. Can you find the inverse Fourier cosine transform of π22ek28\frac{\sqrt{\pi}}{2\sqrt{2}} e^{-\frac{k^2}{8}}?
  4. How would the result change if the exponential function were eax2e^{-ax^2} with a different aa?
  5. What is the physical interpretation of the Fourier transform in this context?
  6. How does the Fourier transform relate to the Laplace transform?
  7. What are some applications of the Fourier cosine transform in engineering?
  8. Can you derive the integral used to evaluate the transform directly?

Tip: When working with Fourier transforms, always consider the function's symmetry properties—they can simplify your calculations significantly.

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Math Problem Analysis

Mathematical Concepts

Fourier Transform
Cosine Transform
Exponential Functions

Formulas

Fourier cosine transform formula
Integral of exponential with cosine

Theorems

Fourier transform properties

Suitable Grade Level

Advanced Mathematics