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1 有兩交流電流,i1(t) = sin(ωt-30°)A,i2(t) =-cos(ωt-30°)A,則i1與i2的相位關係為何? 101 統測
A i1與i2同相位
B i1相位超前i2 30°
C i1相位超前i2 60°
D i1相位超前i2 90°

θ1=-30°

-cos(ωt-30°) = cos(ωt-30°-180°) = sin(ωt-30°-180°+90°) = sin(ωt-120°)

θ2=-120°

故 i1相位超前 i2 90°