Transforms and its Applications: UNIT 4: Fourier Transform

Fourier Cosine Transform and its Inversion formula

Fourier Transform: Formula, Statement, Example Important Solved Problems with formula, steps, derivation and answer based on Fourier cosine transform and its inversion formula.

 

INVERSION FORMULA FOR FOURIER COSINE TRANSFORM

 

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


 

Formula:



Problems based on Fourier cosine transform and its inversion formula

 

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


Transforms and its Applications: UNIT 4: Fourier Transform



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