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Câu 31:

Cho tứ diện đều ABCD, M là trung điểm của cạnh BC. Khi đó $\cos \left( {AB,DM} \right)$

Câu 31: Cho tứ diện đều ABCD, M là trung điểm của cạnh BC. Khi đó cos⁡(AB,DM)\cos \left( {AB,DM} \right)cos(AB,DM) bằng

Thông tin câu hỏi

Câu 31:

Cho tứ diện đều ABCD, M là trung điểm của cạnh BC. Khi đó $\cos \left( {AB,DM} \right)$ bằng