已知|OA|=|a|=3,|OB|=|b|=3,∠AOB=60°,则|a+b|= _ .

问题描述:

已知|

OA
|=|a|=3,|
OB
|=|b|=3
,∠AOB=60°,则|
a
+
b
|= ___ .

|

a
+
b
|2=
a
2
+2
a
b
+
b
2

=9+2|
a
||
b
|cos60°
+9=27
|
a
+
b
|=3
3

故答案为3
3