题干
若 tan α=3,α∈(0,
) ，则 cos (α−
)= ____.
| π |
| 2 |
| π |
| 4 |
答案(点此获取答案解析）
| 2 |
| 5 |
| 5 |
| π |
| 2 |
| π |
| 4 |
| 2 |
| 5 |
| 5 |
