问题
填空题
12．在平行六面体ABCD-A1B1C1D1中，M为AC与BD的交点，若
|
答案
由题意得
| B1M |
| B1A1 |
| A1A |
| AM |
=
| B1A1 |
| A1A |
| 1 |
| 2 |
| AC |
=
| B1A1 |
| A1A |
| 1 |
| 2 |
| AB |
| AD |
=-
| a |
| c |
| 1 |
| 2 |
| a |
| b |
=-
| 1 |
| 2 |
| a |
| 1 |
| 2 |
| b |
| c |
故答案为-
| 1 |
| 2 |
| a |
| 1 |
| 2 |
| b |
| c |
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12．在平行六面体ABCD-A1B1C1D1中，M为AC与BD的交点，若
|
由题意得
| B1M |
| B1A1 |
| A1A |
| AM |
=
| B1A1 |
| A1A |
| 1 |
| 2 |
| AC |
=
| B1A1 |
| A1A |
| 1 |
| 2 |
| AB |
| AD |
=-
| a |
| c |
| 1 |
| 2 |
| a |
| b |
=-
| 1 |
| 2 |
| a |
| 1 |
| 2 |
| b |
| c |
故答案为-
| 1 |
| 2 |
| a |
| 1 |
| 2 |
| b |
| c |