$ e^{2jt} --> system --> te^{-2jt} $
$ e^{-2jt} --> system --> te^{2jt} $
=>$ \cos(2t) $ --> system
=$ \frac{e^{2jt}+e^{-2jt}}{2} $ --> system
=$ \frac{1}{2}(e^{2jt}+e^{-2jt}) $ -->system
=$ \frac{1}{2}e^{2jt}-->system +\frac{1}{2}e^{-2jt}-->system <br> =<math>\frac{1}{2}te^{-2jt} +\frac{1}{2}te^{2jt}<br> =<math>\frac{1}{2}t(e^{-2jt} +e^{2jt})<br> =<math>\frac{1}{2}t\cos(2t)<br> $
