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以几何图形为载体的组合题,直接求解不易奏效,这时我们要认真思考,进行转化,把它转化为与它等价的且容易解答的问题,从而使原问题得解.问题的转化应注意三点:(1)注意联想,运用有关知识,为转化奠定基础;(2)加强分析,确定方向,为转化开路;(3)注意掌握方法,为转化提供措施.现通过例题加以说明.例1正方体的8个顶点的连线中,异面直线共有多少对.分析一个三棱锥各组对棱所在直线异
The combination problem with geometry as a carrier is not easy to be solved directly. At this moment, we should think carefully and transform it into equivalent and easy-to-answer questions so that the original problem can be solved. Pay attention to three points: (1) pay attention to Lenovo and apply the relevant knowledge to lay the foundation for conversion; (2) strengthen analysis, determine the direction and open the way for conversion; (3) pay attention to methods and provide measures for conversion. Example 1 cube eight vertices in the connection, the total number of pairs of different straight lines.Analysis of a triangular pyramid on the line where the edge is different