α垂直(α-2β)
=>α.(α-2β)=0
=>|α|^2 - 2α.β =0
1-2α.β =0
α.β =1/2
|2α+β|^2 = (2α+β).(2α+β)
= 4|α|^2+|β|^2 + 4α.β
= 4+4+4(1/2)
= 10
|2α+β| =√10
α垂直(α-2β)
=>α.(α-2β)=0
=>|α|^2 - 2α.β =0
1-2α.β =0
α.β =1/2
|2α+β|^2 = (2α+β).(2α+β)
= 4|α|^2+|β|^2 + 4α.β
= 4+4+4(1/2)
= 10
|2α+β| =√10