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问题1以正方体的顶点为顶点的三棱锥有多少个?(人教版第二册下B第132页第2题)分析从8个顶点中任取4个点有C84种取法,但正方体的六个表面中的四个点以及
QUESTION 1 How many of the three pyramids are the vertices of the cube? (PEP II, page 132, item 2) Analysis The C84 method takes four points out of the eight vertices, but the cube’s Four of the six surfaces as well