问题:
若
a
与
b
夹角为120°, |
a
|=
3
2
,|
b
|=5,则 |2
a
-
b
|=______.
若
与
夹角为120°, |
|=
,|
|=5,则 |2
-
|=______.
a |
b |
a |
3 |
2 |
b |
a |
b |
参考答案: