The foods pyramid for older adult is wider than that for the young adults
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Dehydration is not a big concern of the older adults
A. 对
B. 错
正弦交流电压u=220sin(ωt-40°)V的有效值相量为。
A. 220/-40°V
B. 155.6/-40°V
C. 220/40°V
D. 155.6/40°V
正弦交流电流i=10sin(ωt+60°)A的最大值相量为。
A. 10/60°A
B. 7.07/-60°A
C. 14.14/60°A
D. 7.07/60°A
正弦交流电压u=400sin(ωt-120°)V的相量为。
A. 282.9/120°
B. 380/-120°
C. 282.9/-120°
D. 400/-120°V
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