正弦波瞬時電壓表示式: `v(t)=V_msin(ωt)`
`V_(rms)=110V ;V_m = 110sqrt(2)V`
`f=60Hz`; `ω = 2πf` `= 2*60*π` `= 120π`
`V_(t)=110sqrt(2) sin(120πt)`