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数学
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正方体ABCD-A1B1C1D1中,点E是D1D的中点,求证D1B‖平面EAC
人气:411 ℃ 时间:2019-12-18 19:55:12
解答
连结AC、BD,交于O,连结EO,
则O是BD的中点,
∵EO是三角形DBD1的中位线,
∴EO//BD1,
∵EO∈平面EAC,
∴D1B//平面EAC.
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