Say I have two signals, one being $g_1(t)$ and the other one being $g_2(t)$, and say that I am being asked to compute the energy of $g_3(t)$, where $$g_3(t) = g_1(t) + g_2(t)$$
Is it correct to compute the energies of $g_1(t)$ and $g_2(t)$ separately and simply add the two values to find $g_3(t)$ or is it correct to compute them as one value? I.e. $$\int_ {-T}^{T} \big[g_1(t)+g_2(t)\big]^2 \,dt $$