I'm stuck on Problem 7 of the 2015 S final exam:
http://forum.math.toronto.edu/index.php?topic=606.0 (link also includes prof's solution)
He gets $$\begin{equation*} \hat{u}(k,t)=-ik (2\pi)^{-1} e^{-k^2a^2 /2} \end{equation*}$$ and he's trying to solve for u(x,t). I don't understand how he gets u(x,t); I know he's using the properties of fourier transforms, but I don't know how to go backward from the fourier transform to the inverse fourier transforms! Thanks
