So, instead of setting up the integral with bounds and integrating dx dy or dy dx or in polar coordinates, I'm just going to say, well, let's remember the definition of a center of mass.
那么我们将不会建立带上下限的积分，和积分dx, dy, dy, dx或者在极坐标做线积分，需要说，让我们回忆一下质心的定义。
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