问题 填空题
已知向量
a
b
满足|
a
|=1,|
b
|=2,|
a
|-|
b
|=2 则等于|
a
|+|
b
|=______.
答案

∵|

a
|=1,|
b
|=2,|
a
|-|
b
|=2,

∴4=1+4-2|

a
||
b
|

∴|

a
||
b
|=
1
2

∴(|

a
|+|
b
|)2=1+4+2|
a
||
b
|=6

∴|

a
|+|
b
|=
6

故答案为:

6

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