How Does the Delta Function and Its Derivative Interact with Shifted Functions?

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gimak
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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


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∫-∞ ∞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
 
Attachments
  • Screenshot of a PDF page from Fourier notes showing the delta function integral identities: integral of delta(x) f(x) dx equals f(0), numbered equation (72), and integral of delta(x - x0) f(x) dx equals f(x0), numbered equation (73).
    upload_2017-7-14_22-37-57.png
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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