问题
填空题
若|
|
答案
若|
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
∴
| a |
| b |
| 15 |
| 2 |
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
可得 cos＜
| a |
| b |
| 1 |
| 2 |
| a |
| b |
故答案为：120°．
搜题请搜索小程序“爱下问搜题”
若|
|
若|
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
∴
| a |
| b |
| 15 |
| 2 |
| a |
| b |
| a |
| b |
| a |
| b |
| a |
| b |
可得 cos＜
| a |
| b |
| 1 |
| 2 |
| a |
| b |
故答案为：120°．