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例题如图1,已知四棱锥P-ABCD的底面ABCD是平行四边形,对角线AC⊥AB,侧棱PA=PB=PC,E,F分别是BC,PD的中点.求证:(Ⅰ)EF∥平面PAB.(Ⅱ)平面PBC⊥平面ABCD.一、平行类问题的处理我们先来分析、解决第(Ⅰ)问.途径1:利用线线平行得到线面平行分析利用直线与平面平行的判定定理证明线面平行,关键是在平面内找到一条直线与已知直线平行,一般有两种途径:构造平行四边形或由中
Example of the problem shown in Figure 1, the known quadrilateral pyramid P-ABCD bottom ABCD is a parallelogram, diagonal AC ⊥ AB, side edges PA = PB = PC, E, F respectively BC, PD midpoint. (Ⅱ) plane PBC⊥ plane ABCD. First, the parallel type of problem processing We first analyze and solve the first (Ⅰ) Q. Path 1: the use of line parallel to get line surface parallel analysis using linear and plane The parallel judgment theorem proves that the lines are parallel. The key is to find a straight line in the plane parallel to the known straight line. Generally, there are two ways: constructing a parallelogram or by