3道高一立体几何证明题17.如图所示,四棱锥P-ABCD的底部为一直角梯形,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.18.如图,在直三棱柱ABC-A,B,C
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![3道高一立体几何证明题17.如图所示,四棱锥P-ABCD的底部为一直角梯形,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.18.如图,在直三棱柱ABC-A,B,C](/uploads/image/z/6236685-45-5.jpg?t=3%E9%81%93%E9%AB%98%E4%B8%80%E7%AB%8B%E4%BD%93%E5%87%A0%E4%BD%95%E8%AF%81%E6%98%8E%E9%A2%9817.%E5%A6%82%E5%9B%BE%E6%89%80%E7%A4%BA%2C%E5%9B%9B%E6%A3%B1%E9%94%A5P-ABCD%E7%9A%84%E5%BA%95%E9%83%A8%E4%B8%BA%E4%B8%80%E7%9B%B4%E8%A7%92%E6%A2%AF%E5%BD%A2%2CBA%E2%8A%A5AD%2CCD%E2%8A%A5AD%2CCD%3D2AB%2CPA%E2%8A%A5%E5%BA%95%E9%9D%A2ABCD%2CE%E4%B8%BAPC%E7%9A%84%E4%B8%AD%E7%82%B9.%EF%BC%881%EF%BC%89%E8%AF%81%E6%98%8E%EF%BC%9AEB%E2%80%96%E5%B9%B3%E9%9D%A2PAD%3B%EF%BC%882%EF%BC%89%E8%8B%A5PA%3DAD%2C%E8%AF%81%E6%98%8E%EF%BC%9ABE%E2%8A%A5%E5%B9%B3%E9%9D%A2PDC.18.%E5%A6%82%E5%9B%BE%2C%E5%9C%A8%E7%9B%B4%E4%B8%89%E6%A3%B1%E6%9F%B1ABC-A%2CB%2CC)
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