题目内容
已知向量a=(
,1),b是不平行于x轴的单位向量,且a·b=
,则b等于( )
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A.![]() |
B.![]() |
C.![]() |
D.(1,0) |
B
方法1:令b=(x,y)(y≠0),则
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将②代入①得
,即
,
∴x=1(舍去,此时y=0)或x=
⇒y=
.
方法2:排除法,D中y=0不合题意;C不是单位向量,舍去;代入A,不合题意,故选B.
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将②代入①得
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∴x=1(舍去,此时y=0)或x=
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方法2:排除法,D中y=0不合题意;C不是单位向量,舍去;代入A,不合题意,故选B.
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