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鞋盒 = kotak kasut 8 个顶点、12 条棱，可能是正方体或长方体；三角棱柱只有 6 个顶点，先排除。鞋盒的面有长方形也有正方形，正方体的面全是正方形，所以不是正方体。答案是长方体。 例子：牙膏盒也是长方体，有长长的长方形面。 注意：正方体也是 8 个顶点 12 条棱，要靠面的形状来分。

shoe box = kotak kasut With 8 vertices and 12 edges, it could be a cube or a cuboid; a triangular prism has only 6 vertices, so rule it out. The shoe box has rectangle faces as well as square ones, while a cube's faces are all squares, so it is not a cube. The answer is a cuboid. Example: a toothpaste box is also a cuboid, with long rectangle faces. Watch out: a cube also has 8 vertices and 12 edges, so tell them apart by the shape of the faces.

球为什么不是棱柱 = mengapa bola bukan prisma 用核对表检查：球没有平的底面，更没有两个一样的底面；它整个表面都是弯的，所以两个条件都不符合，不是棱柱。大小跟是不是棱柱没有关系；说它有两个平的底面是错的。 例子：西瓜、地球仪也都是球体，不是棱柱。 注意：解释“不是棱柱”时，要说出哪个条件不符合。

why a ball is not a prism = mengapa bola bukan prisma Use the checklist: a ball has no flat base, let alone two matching bases, and its whole surface is curved, so it fails both conditions and is not a prism. Size has nothing to do with being a prism, and saying it has two flat bases is wrong. Example: a watermelon and a globe are spheres too, not prisms. Watch out: when explaining why something is not a prism, name the condition it fails.

五条对称轴 = 5 paksi simetri 正多边形的对称轴条数等于边数。要 5 条对称轴，就要 5 条边，也就是正五边形 pentagon。正六边形有 6 条，正方形有 4 条，都不是 5 条。 例子：要 8 条对称轴 → 8 条边 → oktagon。 注意：这个规律只适用于正多边形。

five lines of symmetry = 5 paksi simetri A regular polygon has as many lines of symmetry as sides. To have 5 lines it needs 5 sides, which makes it a regular pentagon. The regular hexagon has 6 lines and the square has 4, so neither has 5. Example: 8 lines of symmetry means 8 sides, an octagon. Watch out: this rule works only for regular polygons.