Household electrical power in the US is provided in the form of alternating current. Typically the voltage cycles smoothly between +155.6 volts and -155.6 volts 60 times per second. Use a sinusoidal function to model the voltage, \(V\), as a function of time, \(t\), in seconds since the voltage was at its peak.

\( V(t)= 155.6\cos \left ( 120\pi t \right ) \)