dt>0是什么意思

0代表什么意思跟沿x轴正方向传播和负方向传播有什么关系吗 dy/dt表示波中介质质点的简谐运动速度,大于零表示此刻的速度沿着+y方向v=dy/dt 0跟波速u方向(沿着x轴)无关,

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