单项选择题
A.3倍 B.9倍 C.1/9 D.1/3
A.u=10sin(314t+30°) B.10√2sin(314t+75°) C.10√2sin(314t+15°) D.20sin(314t-15°)
A.同相位 B.相位彼此相差30° C.相位彼此相差120° D.相位彼此相差90°
A.20h B.40h C.45h D.25h
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