题目内容
在△ABC中,点D是边AC的中点,
=
,
=
,那么用
、
表示
,
=______.
| BA |
| a |
| BC |
| b |
| a |
| b |
| BD |
| BD |
∵在△ABC中,点D是边AC的中点,
∴AD=
AC,
∵
=
,
=
,
∴
=
-
=
-
,
∴
=
=
(
-
),
∴
=
+
=
+
(
-
)=
+
.
故答案为:
+
.

∴AD=
| 1 |
| 2 |
∵
| BA |
| a |
| BC |
| b |
∴
| AC |
| BC |
| BA |
| b |
| a |
∴
| AD |
| 1 |
| 2 |
| AC |
| 1 |
| 2 |
| b |
| a |
∴
| BD |
| BA |
| AD |
| a |
| 1 |
| 2 |
| b |
| a |
| 1 |
| 2 |
| a |
| 1 |
| 2 |
| b |
故答案为:
| 1 |
| 2 |
| a |
| 1 |
| 2 |
| b |
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