Compute the inverse fourier transform of the fourier transform below:
$ \,\mathcal{X}(\omega)= \delta(\omega - 3\pi) e^{-t}\, $
$ \,x(t)=\frac{1}{2\pi}\int_{-\infty}^{\infty}\mathcal{X}(\omega)e^{j\omega t}\,d\omega \, $
