Explanation

(a) The instantaneous value of voltage is
$E = 100\sin{(100t)}V\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ldots(i)$
Compare it with $E = E_{0}\sin{(\omega t)}V$
We get
$E_{0} = 100V,\ \omega = 100rads^{- 1}$
The $rms$ value of voltage is
$E_{rms} = \frac{E_{0}}{\sqrt{2}} = \frac{100}{\sqrt{2}}V = 70.7V$
The instantaneous value of current is
$I = 100\sin\left( 100t + \frac{\pi}{3} \right)mA$
Compare it with
$I = I_{0}\sin(\omega t + \phi)$
We get
$I_{0} = 100mA,\ \omega = 100rads^{- 1}$
The $rms\ $value of current is
$I_{rms} = \frac{I_{0}}{\sqrt{2}} = \frac{100}{\sqrt{2}}mA = 70.7mA$