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thientrieu96ht
2 năm trước
Giúp mình với :((( Bài 3. Cho hình chóp S.ABCD có đáy ABCD là hình chữ nhật; SA vuông góc (ABCD). Cạnh SC = a hợp với đáy góc α và hợp với mặt bên (SAB) góc β. a) Tính SA. b) CMR: AB = a. căn của [cos(α+β).cos(α-β)]
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