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Cho hình hộp ABCD.A’B’C’D’ có các cạnh bằng a, góc BAD=60 độ, BAA'=DAA'=120 độ a) Tính góc giữa các cặp đường thẳng AB với A’D và AC’ với B’D b) Tính góc giữa đường thẳng AC’ và các đường thẳng AB, AD, AA
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