如图,在三棱柱ABC-A1B1C1中,侧棱AA1⊥底面ABC,AB⊥AC,BC=1,AB=2,BB1=2,点E是棱CC1中点.(1)求证

2025-04-29 21:59:22
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回答1:

(1)证明:∵AA1⊥底面ABC,AA1∥BB1
∴BB1⊥底面ABC,∴AB⊥BB1,又AB⊥BC
∴AB⊥BB1C1C,∴AB⊥EB1
EB2+FB12=BB12,∴EB1⊥EB
∴EB1⊥平面ABE              
(2)解:分别以射线BA、BC、BB1为x轴、y轴、z轴正半轴建立空间直角坐标系B-xyz
则B(0,0,0),A(

2
,0,0),E(0,1,1),A1(
2
,0,2),B1(0,0,2)

由(1)知平面ABE的法向量为
EB1
=(0,?1,1)

设平面AA1E的法向量为
m
=(x,y,z)
,又
AA1
=(0,0,2),
A1E
=(?
2
,1,?1)