Fourier Transform: Formula, Statement, Example Important Solved Problems with formula, steps, derivation and answer based on Fourier cosine transform and its inversion formula.
Let
FC(s) denote the F.C.T of f(x).
Then

Proof: By
the definition of F.C.T,

Here,
f(x) is defined for all x ≥0
Now
define g(x) by g(x) = 
Clearly,
g(‒x)
= g(x) for all x and hence g is an even function.
To
prove that, the Fourier transform of g(x) is the F.C.T of f(x).

=
Fc [g(x)]
=
Fc [f(x)] [ g(x) = f(x) for all x ≥ 0]
Hence,
by inversion formula for F.T, we have


Example 1: Solve the integral equation
and also show that
.
Solution:

Example 2: Solve the integral equation

Solution:


Example 3: Find the Fourier cosine transform
of e‒|x| and deduce that
.
Solution:
We know that,

Example 4: Find the Fourier cosine transform
of e-ax, a>0 and deduce that
.
Solution:
We know that,

Applying
the inversion formula, we have

Transforms and its Applications: UNIT 4: Fourier Transform : Tag: Engineering mathematics, Maths : - Fourier Cosine Transform and its Inversion formula
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