If those two branches in turn each split into two branches, the area of the cross sections of the four additional branches together will equal the area of the cross section of the trunk. And so on.
这条的规律可以简单描述为：如果一根树干分叉为两个树枝，那么两个树枝的横截面积之和等于树干的横截面积；如果树枝接着分别分叉为两根小树枝，那么这四个次生分枝的横截面积总和仍等于树干的横截面积……依此类推。
The four-point bearing (also see page 9) is suitable for accommodating tilting forces at a small cross-section.
四点轴承（也请参见第9页）是容纳在一个小截面适当倾斜力量。
Their conical sphenoid part, for the configuration of which at least four conical surfaces are used, can have the same cross section all over its length or different cross-section per parts.
圆锥楔形体的结构至少有四个圆锥面组成，在每个面上，可以使用相同的横截面，也可用不同的横截面。
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