Let XXX have the PDF f(x)=12e−∣x∣f(x) = \frac{1}{2}e^{-|x|}f(x)=21e−∣x∣. What is the Characteristic Function ϕ(t)\phi(t)ϕ(t)?
(1+t2)−1(1+t^2)^{-1}(1+t2)−1
e−t2/2e^{-t^2/2}e−t2/2
(1−it)−1(1-it)^{-1}(1−it)−1
(1+it)−1(1+it)^{-1}(1+it)−1