a) Damping by friction often leads to exponentially-decaying functions, such as
f(x)=exp(-a|x|),a>0
. Show that the Fourier transform,
g(k)=(1)/(2\pi )\int e^(ikx)f(x)dx
, of this function is a Lorentzian, i.e.
∼(1)/(a^(2)+k^(2))
.