谈谈楔形
楔形的英文叫wedge,这是一个什么样的几何体呢?
且看*的解释:
In solid geometry, a wedge is a polyhedron defined by two triangles and three trapezoid faces. A wedge has five faces, nine edges, and six vertices.
A wedge is a subclass of the prismatoids with the base and opposite ridge in two parallel planes.
A wedge can also be classified as a digonal cupola.
Comparisons:
A wedge is a parallelepiped where a face has collapsed into a line.
A quadrilaterally-based pyramid is a wedge in which one of the edges between two trapezoid faces has collapsed into a point.
楔形大致就上面图中的样子,两个三角形和三个四边形,不过要求四边形为梯形,实际上要求满足其中三条边是平行的,哪三条边呢?就是图上看到的是水平的那三条边。这是硬性条件,否则不能称之为楔形。
三棱柱是特殊的楔形。
图中的底边是一个矩形,这只是一个特例,并不是所有的楔形都要求有一个四边形为矩形。