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2001年北京,内蒙古,安徽春季高考选择题中,似以如下一题为较难: 图1是正方体的平面展开图,在这个正方体中,①BM与ED平行; ②CN与BE是异面直线; ③CN与BM成60°角; ④DN与BN垂直. 以上四个命题中,正确命题的序号是 (A)①②③(B)②④ (C)③④(D)②③④ 正确的解法是对①②③④各命题一一判定其真假,然后与选择支对照,作出正确选择.“快捷解法”则可用“攻其一点不及其馀”的方法,选好了突破口,例如如发现④是假命题则(B)(C)(D)全不对,径可选(A).而如发现②
In the 2001 Beijing, Inner Mongolia, and Anhui spring college entrance examination multiple-choice questions, the following question appears to be more difficult: Figure 1 is a flat development of a cube in which the 1BM is parallel to the ED; 2CN and BE are non-planar straight lines; 3CN The angle is 60° with BM; 4DN is perpendicular to BN. Among the above four propositions, the correct proposition number is (A) 123 (B) 24 (C) 34 (D) 234 The correct solution is to determine each proposition of 1234 one by one. It is true and false, and then compared with the choice support, make correct choices. The “quick solution” can use the method of “attacking one point but not others” to select the breakthrough point. For example, if it is found that 4 is a false proposition, then (B) (C) (D) All wrong, trail selectable (A). And if found 2