Solution
= Solution
Set $\alpha=1$ in part (d), obtaining $\mathcal F[e^{-|t|}](\omega)=2/(1+\omega^2)$. Apply the <duality property of the Fourier transform> from part (a):
$$
2\mathcal F\left[\frac1{1+t^2}\right](\omega)
=2\pi e^{-|\omega|}.
$$
Therefore
$$
\boxed{\widetilde s(\omega)=\pi e^{-|\omega|}}.
$$