Pr$4.$ Use phasor analysis to: $($a$)$ Draw the equivalent circuit in phasor domain. Find is $(t)$ and $i_1(t)$ in the following circuit, given that $v_s(t)=20cos(2{10}^{4}t+45)V,R_1=2k,R_2=1k,L=150mH,$ and $C=25$ nF $.($b$)$ Find the volatge across the resostor R$1.($c$)$ Write the expression of calculating the instantaneous power of the power supply without any calculation.

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