Delta function properties

In summary, we are proving the equation ∫-∞∞δ'(x)*f(x-a) = -f'(a) using the equation ∫-∞∞δ'(x-a)*f(x) = f(a) and the method of integration by parts.
  • #1
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Homework Statement


Prove the following
'()( − ) = −′()
-∞δ'(x)*f(x-a) = -f'(a)

Homework Equations


-∞δ'(x-a)*f(x) = f(a)

The Attempt at a Solution


[/B]
-∞ δ'(x)*f(x-a) = ∫δ(x)*f(x-a)dx-∫f'(x-a)*δ(x)dx = f(-a) - f'(-a)
Went from 1st to second by integration by parts
Used integral definition of delta function to go to 3rd part
 

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  • #2

The Attempt at a Solution



1) ∫-∞ ∞δ'(x)*f(x-a)
2) = ∫δ(x)*f(x-a)dx-∫f'(x-a)*δ(x)dx
3) = f(-a) - f'(-a)
Went from 1st to second by integration by parts
Used integral definition of delta function to go to 3rd part

Made above easier to read
 

1. What is the definition of a delta function?

A delta function, denoted by δ(x), is a mathematical function that is zero everywhere except at x=0, where it is infinite. It is often used in mathematical modeling to represent a point-like or infinitely narrow quantity.

2. What are the key properties of the delta function?

The key properties of the delta function include its symmetry (δ(x) = δ(-x)), its scaling property (δ(ax) = 1/|a|δ(x)), and its sifting property (∫f(x)δ(x-a)dx = f(a)). It also has a total area of 1 and can be used to represent impulses or point sources in physical systems.

3. How is the delta function related to the Dirac delta function?

The delta function is often used as a shorthand for the Dirac delta function, named after physicist Paul Dirac. The Dirac delta function is a generalized function that can be thought of as the limit of a sequence of functions that approach the delta function as the parameter approaches 0.

4. Can the delta function be integrated or differentiated?

The delta function is not a traditional function, so it cannot be integrated in the traditional sense. However, it can be integrated as part of a larger function using the sifting property. It can also be differentiated in the sense of distribution theory, which involves integrating against a test function.

5. In what fields of science is the delta function commonly used?

The delta function is commonly used in fields such as physics, engineering, and signal processing. It is used to represent point sources and impulses in physical systems, and is also useful in solving differential equations and modeling systems with discontinuities. It is also used in probability and statistics to represent probability distributions with point masses.

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