Various forms of pyramids may be used, however pyramids with planar faces are most suitable.
可以使用各种形式的金字塔，但具有平的表面的金字塔是最适合的。
The constraint in the value of N<6,82 can be overcome if the planar faces of the cube become spherical parts of long radius.
如果把立方体的纯平面换成球形面，那么这个N<6.82的约束就可以解决。
A mineral, especially a transparent form of quartz, having a crystalline structure, often characterized by external planar faces.
水晶一种具有晶体结构的矿石，尤指石英的一种透明形态，通常其晶面在同一平面上。
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