如图,已知平行六面体ABCD—A1B1C1D1的底面ABCD是菱形且∠C1CB=∠C1CD=∠BCD=60°.
(1)证明:C1C⊥BD;
(2)假定CD=2,CC1=,记面C1BD为α,面CBD为β,求二面角α—BD—β的平面角的余弦值;
(3)当的值为多少时,能使A1C⊥平面C1BD?请给出证明.
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如图,已知平行六面体ABCD—A1B1C1D1的底面ABCD是菱形且∠C1CB=∠C1CD=∠BCD=60°.
(1)证明:C1C⊥BD;
(2)假定CD=2,CC1=,记面C1BD为α,面CBD为β,求二面角α—BD—β的平面角的余弦值;
(3)当的值为多少时,能使A1C⊥平面C1BD?请给出证明.