题目内容
设点O是△ABC的外心，AB=13，AC=12，则
•
=______．
| BC |
| AO |
过O作OS⊥AB，OT⊥AC垂足分别为S，T 则S，T分别是AB，AC的中点，
•
=(
+
)•
=
•
+
•
=-|
||
|+|
|•|
|=-13×
+12×
=-
故答案为：-
| BC |
| AO |
| BA |
| AC |
| AO |
| BA |
| AO |
| AC |
| AO |
=-|
| BA |
| AS |
| AC |
| AT |
| 13 |
| 2 |
| 12 |
| 2 |
=-
| 25 |
| 2 |
故答案为：-
| 25 |
| 2 |
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设点O是△ABC的外心，AB＝13，AC＝12，则·＝ ．
= ．