[填空题]
Suppose a current is given by te // m4+e:x:tmvi1lpyfn. jd qqc7; ww;lnj 6xn:q+vmhqo6 3 m kzi/h*he equation $I\,=\,1.80sin210t$, where I is in amperes and t in seconds.
(a) What is the frequency? Hz
(b) What is the rms value of the current? A
(c) If this is the current through a $42-\Omega$ resistor, write the equation that describes the voltage as a function of time. ( sin 210 t)V
