# energy/power signals

I have the two signals and need to determine whether they are energy type or power type: $$x_1(t)=A\cos(2\pi ft), -\infty<t<\infty$$ $$x_2(t)=1$$

I have solved the first one using the expression for the energy of the signal and found that energy is infinite so it must be a power signal. For the second one I don't know how to solve that as I don't know what limits to use.Any help will be appreciated.

• If no limits are given, I would assume plus/minus infinity as well. Or zero to infinity since it's about time....But it won't change the answer. – Eugene Sh. Feb 12 '18 at 19:14

$$E_2 = \int_{-\infty}^{+\infty}{|x_2(t)|^2}dt = \int_{-\infty}^{+\infty}dt = \lim_{T \,\to\, +\infty} \int_{-T/2}^{T/2}dt= +\infty$$