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九四年高考题23题,是一道考查基础知识与考查能力并重的好题 。其第(Ⅱ)题的计算结果实质上给出了侧面对角线垂直的正三棱柱的一个性质。我们对此三棱柱作了一般分析和研究,这里,我们将其有关性质整理出来,并给出证明,供同行参考。 如图1,已知A_1B_1C_1—ABC是正三棱柱,其侧面对角线BC_1⊥AB_1,以此为条件可
The ninety-four college entrance examination question 23 is a good question that examines both basic knowledge and examination ability. The calculation result of the (II) question essentially gives a property of a normal trigonal prism whose side diagonal is vertical. We have made a general analysis and study of this tri-prism. Here, we will sort out its relevant properties and give proofs for the reference of our peers. As shown in Figure 1, it is known that A_1B_1C_1-ABC is a positive trigonal prism whose lateral diagonal is BC_1⊥AB_1.