题目内容
下列命题正确的是( )
分析:利用数量积运算即可得出.
解答:解:对于B:∵|
+
=|
-
|,
∴
2+
2+2
•
=
2+
2-2
•
,
∴
•
=0.
故选B.
| a |
| b| |
| a |
| b |
∴
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
∴
| a |
| b |
故选B.
点评:熟练掌握数量积运算是解题的关键.
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