$ f(t)=j*5*sin(t) $
$ E_\infty = \int_{-\infty}^\infty |5sin(t)|^2\,dt) $
$ E_\infty = \int_{-\infty}^\infty 25sin(t)^2u(t)\,dt) $
$ E_\infty = \int_{-\infty}^\infty 25(.5 + .5cos(2t)),dt) $
$ E_\infty =\frac{t}{2} + \frac{sin(t)}{4}\bigg]_-infty^\infty) $
$ E_\infty =\infty-0 = \infty $
