Signal
$ x(t) = e^{jt} $
Energy
$ E_\infty = \int_{-\infty}^\infty |x(t)|^2dt $
$ = \int_{-\infty}^\infty |e^{jt}|^2dt $
$ = \int_{-\infty}^\infty |cos(t) + jsin(t)|^2dt $ (Euler's Formula)
$ = \int_{-\infty}^\infty {\sqrt{cos^2(t) + sin^2(t)}}^2dt $ (Magnitude of a Complex Number)
$ = \int_{-\infty}^\infty dt $
$ = t|_{-\infty}^\infty $
$ = \infty - (-\infty) $
$ = \infty $
