And so it will be a surface integral, not a line integral anymore.
所以要用面积分，而非线积分。
It is a surface integral, so we need to have two variables in there.
它是一个面积分，所以这里需要两个变量。
OK, and that surface integral, well, it's not for the same vector field.
这个曲面积分，不是同一个向量场。
OK, and that surface integral, well, it's not for the same vector field.
这个曲面积分，不是同一个向量场。
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