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题目如图1,已知三棱锥A—BCD 的侧棱 AD 垂直于底面BCD,侧面 ABC 与底面所成的角为θ,求证:V_(三棱锥)=1/3S_(△ABC)·AD
The problem is shown in Fig. 1. The side edge AD of the known pyramid A-BCD is perpendicular to the bottom BCD. The angle formed by the side ABC and the bottom is θ. Verify that V_(triangles)=1/3S_(△ABC)·AD