如图,在正方体ABCD-A1B1C1D1中,E、F分别是BB1、DC的中点.(Ⅰ)求异面直线AE与D1F所成的角;(Ⅱ)证

2025-05-14 19:31:17
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解答:(Ⅰ)解:如图,设正方体的棱长为1,建立空间直角坐标系D-xyz,
则A(1,0,0),E(1,1,

1
2
),F(0,
1
2
,0),D1(0,0,1),
AE
=(0,1,
1
2
)
D1F
=(0,
1
2
,?1)

AE
?
D1F
=0,∴
AE
D1F

∴异面直线AE与D1F所成的角为90°.
(Ⅱ)证明:∵
DA
D1A1
=(1,0,0)

D1A1
?
AE
=0

∴AE⊥D1A1,由(Ⅰ)知AE⊥D1F,且D1F∩D1A1=D1
∴AE⊥平面A1D1F.