Is $\delta\left(a+bi\right)=\delta\left(a-bi\right)$? I wonder whether Dirac Delta (as defined via Fourier transform) is symmetric against the real axis. We can write Delta function as $$\delta(z) = \frac{1}{2\pi}\int_{-\infty}^\infty e^{itz}\, dt=\delta\left(a+bi\right)=\frac1{2\pi}\int_{-\infty}^{+\infty}e^{-bx}\cos ax\, dx+\frac{i}{2\pi}\int_{-\infty}^{+\infty}e^{-bx}\sin ax\, dx.$$ The second integral is always zero (using Abel regularization), the first integral does not depend on the sign of $b$. So, $\delta\left(a+bi\right)$ should be equal to $\delta\left(a-bi\right)$. But this contradicts [the fact that][1] $$\int_{-\infty}^\infty \delta(t+bi)f(t)dt=f(-bi)$$ which depends on the sign of $b$. I have [asked][2] this on Math.Stackexchange, but received no answers. [1]: https://math.stackexchange.com/a/4045521/2513 [2]: https://math.stackexchange.com/questions/4046093/is-delta-leftabi-right-delta-lefta-bi-right