30.若電壓v(t)＝50sin(?t＋45°)V，電流i(t)＝10cos(?t－45°)A，則下列何者錯誤？
(A) v(t)領先i(t) 90°
(B) v(t)落後i(t) 90°
(C) v(t)領先i(t) 180°
(D) v(t)與i(t)同相

答案：✅ (A)、(B)、(C) 解析...