已知向量=(1,2),
=(
2,
4),|
|=
,若(
)・
=
,则
与
的夹角为
A.30° B.60° C.120° D.150°
已知向量=(1,2),
=(
2,
4),|
|=
,若(
)・
=
,则
与
的夹角为
A.30° B.60° C.120° D.150°
C