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长(正)方体是立体几何中最常见也是最具特性的几何体之一,各种点、线、面间的位置关系都有体现.如果在解题中能构造出长(正)方体,可使图形丰满完善,降低思维难度,直观简捷地解决问题.一、判断位置关系例1已知异面直线α与b不垂直,关于α、b在平面内的射影的可能情况给出以下结论:①是两条平行线;②是两条互相垂直的直线;③是一条直线及其外的一点;④是同一条直线.其
The long (positive) cube is one of the most common and most characteristic geometric bodies in solid geometry, and the position relationships among various points, lines and planes are all represented. If long , Can make plump and perfect graphics, reduce the difficulty of thinking, intuitive and simple solution to the problem.One, to determine the location relationshipExample 1 Known different surface straight line α and b are not vertical, on α, b in the plane of the projective probability given the following Conclusion: ① is the two parallel lines; ② is two straight lines perpendicular to each other; ③ is a straight line and a little outside; ④ is the same straight line.