Convert the following pairs of voltage and current waveforms to phasor form. Each pair of waveforms corresponds to an unknown element. Determine whether each element is a resistor, a capacitor, or an inductor, and compute the value of the corresponding parameter R, C, or L v(t)= 20 cos(400t + 1.2), i(t)= 4 sin(900t +1.2) v(t)= 9 cos(900t - π/3 ), i(t)= 4 sin(900t + 2/3π) v(t)= 13 cos(250t + π/3 ), i(t)= 7 sin(250t + 5/6π)