The Power Instantaneous P(t) on the Element When the Current

Short Answer

the power instantaneous p(t) on the element when the current i(t) through the element
from positive terminal to negative terminal and voltage v(t) across the element are given by $$\mathrm { i } ( \mathrm { t } ) = 12 \cos \left( 2 \pi 50 \mathrm { t } + 50 ^ { \circ } \right) \mathrm { A } , \mathrm { v } ( \mathrm { t } ) = 210 \cos \left( 2 \pi 50 \mathrm { t } + 75 ^ { \circ } \right) \mathrm { V }$$