该书大部分都是关于他们实际存在一些的问题—外扩的线条，垂曲弧，穹型拱顶。

Much of the book is about their practical problems-thrust lines, the catenary curve and groin vaulting.

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在双曲空间中，考察椭圆的包含关系，对弧长元素、测地曲率、曲率、面积及全曲率等几何量做出细致考察。

Some geometric data of ellipse in hyperbolic space are considered, such as set inclusion, arc length, geodesic curvature, curvature, area and total curvature.

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