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hoangan16122000
2 năm trước
Cho hình chóp có đáy ABCD là hình thang vuông tại B và C, CD = 2AB, AD = a, góc ADC = 30 độ, SA vuông góc với mặt phẳng đáy và SA = 2a. Khoảng cách từ D đến mặt phẳng (SBC) bằng A. (căn 57 x a)/19 B. (2 căn 57 x a)/19 C. ( 4 căn 57 x a)/19 D. a căn 3
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