如图所示:四棱锥P-ABCD底面一直角梯形,BA⊥AD,CD⊥AD,CD=2AB,PA⊥底面ABCD,E为PC的中点.
(1)证明:EB∥平面PAD;
(2)若PA=AD,证明:BE⊥平面PDC;
(3)当PA=AD=DC时,求二面角E-BD-C的正切值.
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如图所示:四棱锥P-ABCD底面一直角梯形,BA⊥AD,CD⊥AD,CD=2AB,PA⊥底面ABCD,E为PC的中点.
(1)证明:EB∥平面PAD;
(2)若PA=AD,证明:BE⊥平面PDC;
(3)当PA=AD=DC时,求二面角E-BD-C的正切值.