问题:
已知 |
a
|=2, |
b
|=1, (
a
+
b
)⊥
b
,则
a
与
b
的夹角是( )
A.150°
B.120°
C.60°
D.30°
已知 |
|=2, |
|=1, (
+
)⊥
,则
与
的夹角是( )
a |
b |
a |
b |
b |
a |
b |
A.150° | B.120° | C.60° | D.30° |
参考答案: