Is there a way to get Mathematica to integrate imaginary exponential functions to give delta functions? Analytically, we obtain:

$$\int_{-\infty}^{\infty} e^{i kx} dk = 2 \pi \delta(x)$$


Integrate[E^(I k x), {k, -\[Infinity], \[Infinity]}]

However, an error saying that the integral does not converge in these limits stops the integral from being evaluated.

  • $\begingroup$ 2023... It's a pity this still would not work, even upon specifying the Assumptions ^_^ $\endgroup$
    – mavzolej
    May 6, 2023 at 20:35

1 Answer 1


For Fourier integrals like this one, use FourierTransform.

FourierTransform[1, k, x, FourierParameters -> {1, 1}]
(* 2 \[Pi] DiracDelta[x] *)

FourierTransform understands that it can use generalized functions like DiracDelta to represent some integrals that don't converge. Integrate can't do that.


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