题目内容
若平面内不共线的四点O，A，B，C满足| OB |
| 1 |
| 3 |
| OA |
| 2 |
| 3 |
| OC |
|
| ||
|
|
分析：用向量的减法法则将
，
用
，
，
表示．将已知条件代入消去
得解．
| AB |
| BC |
| OB |
| OA |
| OC |
| OB |
解答：解：∵
=
-
，
=
-
∵
=
+
∴
=
+
-
=
-
=
-
-
=
-
∴
=
=2
故答案为2
| AB |
| OB |
| OA |
| BC |
| OC |
| OB |
∵
| OB |
| 1 |
| 3 |
| OA |
| 2 |
| 3 |
| OC |
∴
| AB |
| 1 |
| 3 |
| OA |
| 2 |
| 3 |
| OC |
| OA |
| 2 |
| 3 |
| OC |
| 2 |
| 3 |
| OA |
| BC |
| OC |
| 1 |
| 3 |
| OA |
| 2 |
| 3 |
| OC |
| 1 |
| 3 |
| OC |
| 1 |
| 3 |
| OA |
∴
|
| ||
|
|
|
| ||||||||
|
|
故答案为2
点评：考查向量的减法法则三角形法则和向量的数乘法则．
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