在正方形ABCD-A1B1C1D1中,求①A1B与AD1所成的角
②BC1与平面DBB1D1所成的角
③求证A1C⊥平面DBC1
人气：158 ℃ 时间：2019-12-20 02:47:51
解答
①A1B与AD1所成的角:D1C‖A1B.⊿AD1C是正三角形（边长都是√2AB）∠AD1C＝60ºA1B与AD1所成的角＝60º②设O是ABCD中心,CO⊥平面DBB1D1 ∴∠CB1O为所求角,CB1＝2CO.∴所求角＝30º③BD⊥AC.BD⊥AA1（∴BD...
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