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Why mathematica doesnt produce any answer to the following integral?

Integrate[0.040608386793220284*DiracDelta[w]*DiracDelta[-w + x], {w, -2, 2}]

and how can I get a solution?

Thank you very much.

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1  
Have a look at 12000 –  b.gatessucks Oct 18 '13 at 14:55
    
@b.gatessucks than you very much –  Seyhmus Güngören Oct 18 '13 at 21:22
    
Thanks @b.gatessucks. –  Seyhmus Güngören Oct 19 '13 at 16:23
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1 Answer 1

Because you are using it incorrectly. The integral of a delta function is 1 when taken over all values:

Integrate[0.0406*DiracDelta[w]*DiracDelta[-w + x], {w, -Infinity, Infinity}]

gives the expected

0.0406 DiracDelta[x]
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but I am interested in the integral only in this range, not from minus infty to plus infty. –  Seyhmus Güngören Oct 18 '13 at 14:59
    
then specify x.. it can't know the value unless it knows x. Observe that Integrate[0.0406*DiracDelta[w]*DiracDelta[-w + 100], {w, -2, 2}] gives 0. –  bill s Oct 18 '13 at 15:18
    
Integrate[f[x - w] DiracDelta[w], {w, -2, 2}, Assumptions -> x [Element] Reals && x [Element] Reals] /. f -> DiracDelta –  Seyhmus Güngören Oct 18 '13 at 16:16
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