问题:
已知|
a
|=1,|
b
|=2,<
a
,
b
>=60°,则|2
a
+
b
|=______.
已知|
|=1,|
|=2,<
,
>=60°,则|2
+
|=______.
a |
b |
a |
b |
a |
b |
参考答案: