题目内容
在△ABC中,A=90°,AB=6,且
=2
,则
•
的值为______.
| CD |
| DB |
| AB |
| AD |
在△ABC中,∵A=90°,AB=6,且
=2
,
∴
•
=
•(
+
)
=
•(
+
)
=
•[
+
(
-
)]
=
•(
+
)
=
•
+
2
=
×0+
•|
|2
=
×62
=24.
故答案为:24.
| CD |
| DB |
∴
| AB |
| AD |
| AB |
| AC |
| CD |
=
| AB |
| AC |
| 2 |
| 3 |
| CB |
=
| AB |
| AC |
| 2 |
| 3 |
| AB |
| AC |
=
| AB |
| 1 |
| 3 |
| AC |
| 2 |
| 3 |
| AB |
=
| 1 |
| 3 |
| AB |
| AC |
| 2 |
| 3 |
| AB |
=
| 1 |
| 3 |
| 2 |
| 3 |
| AB |
=
| 2 |
| 3 |
=24.
故答案为:24.
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