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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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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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  • $\begingroup$ but I am interested in the integral only in this range, not from minus infty to plus infty. $\endgroup$ – Seyhmus Güngören Oct 18 '13 at 14:59
  • $\begingroup$ 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. $\endgroup$ – bill s Oct 18 '13 at 15:18
  • $\begingroup$ Integrate[f[x - w] DiracDelta[w], {w, -2, 2}, Assumptions -> x [Element] Reals && x [Element] Reals] /. f -> DiracDelta $\endgroup$ – Seyhmus Güngören Oct 18 '13 at 16:16

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