若曲面\(\sum\)为平面\(x = 0,y = 0,z = 0\)及平面\(x + y + z = 1\)所围成的四面体的整个边界曲面，则曲面积分\(\int\!\!\!\int\limits_\Sigma {xyzdS = {1 \over {40}}} \) 。
若曲面\(\sum\)为平面\(x = 0,y = 0,z = 0\)及平面\(x + y + z = 1\)所围成的四面体的整个边界曲面，则曲面积分\(\int\!\!\!\int\limits_\Sigma {xyzdS = {1 \over {40}}} \) 。
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