如图,四棱柱ABCD—A1B1C1D1的底面边长和侧棱长都等于2,平面A1ACC1⊥平面ABCD,∠ABC=∠A1AC=60°,点O为底面对角线AC与BD的交点.
(Ⅰ)证明:A1O⊥平面ABCD;
(Ⅱ)求二面角D—A1A—C的平面角的正切值.
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如图,四棱柱ABCD—A1B1C1D1的底面边长和侧棱长都等于2,平面A1ACC1⊥平面ABCD,∠ABC=∠A1AC=60°,点O为底面对角线AC与BD的交点.
(Ⅰ)证明:A1O⊥平面ABCD;
(Ⅱ)求二面角D—A1A—C的平面角的正切值.