题目
(sin
−sin
)(sin
+sin
)
| 5π |
| 12 |
| π |
| 12 |
| 5π |
| 12 |
| π |
| 12 |
提问时间：2021-01-29
答案
原式=[sin（
−
）-sin
][sin（
−
）+sin
]
=（cos
-sin
）（cos
+sin
）
=cos2
-sin2
=cos
=
| π |
| 2 |
| π |
| 12 |
| π |
| 12 |
| π |
| 2 |
| π |
| 12 |
| π |
| 12 |
=（cos
| π |
| 12 |
| π |
| 12 |
| π |
| 12 |
| π |
| 12 |
=cos2
| π |
| 12 |
| π |
| 12 |
| π |
| 6 |