如图所示, 平面 PAB⊥平面 ABCD, 底面 ABCD 是边长为 8 的正方形, ∠APB=90° , 点 E, F分别是 DC, AP 的中点.(1) 证

如图所示, 平面 PAB⊥平面 ABCD, 底面 ABCD 是边长为 8 的正方形, ∠APB=90° , 点 E, F分别是 DC, AP 的中点.(1) 证明: DF∥平面 PBE;(2) 若 A

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Whenever Mary reads an interesting story, she can’t keep it to _____ and wants t

Whenever Mary reads an interesting story, she can’t keep it to _____ and wants to share it with her

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In order to save the energy, we should ________ lights in time if we don’t need

In order to save the energy, we should ________ lights in time if we don’t need them.

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This is one of the highest buildings that ________ in our city recently.

This is one of the highest buildings that ________ in our city recently.

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