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Tranlamkh
2 năm trước
Cho hình chóp S.ABC có đáy ABC là tam giác vuông tại B, AB=2a, BC=2a căn . Cạnh SA vuông góc với mặt phẳng (ABC). Đường SB tạo với (ABC) góc 60 độ. Với N là trung điểm của AC. Tính cosin góc giữa 2 đường thẳng SN và BC
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