For personal use only in study and research; not for commercial use
1.在三棱锥
<Object: word/embeddings/oleObject1.bin>
中，△<Object: word/embeddings/oleObject2.bin>
是边长为
<Object: word/embeddings/oleObject3.bin>
的正三角形，平面
<Object: word/embeddings/oleObject4.bin>
平面<Object: word/embeddings/oleObject5.bin>
，<Object: word/embeddings/oleObject6.bin>
、<Object: word/embeddings/oleObject7.bin>
分别为<Object: word/embeddings/oleObject8.bin>
的中点。
（Ⅰ）证明：
<Object: word/embeddings/oleObject9.bin>
⊥<Object: word/embed ...