（sin10＋sin50）/（sin35×sin55）的值详细过程详细
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解决时间 2021-02-10 18:51
- 提问者网友：刺鸟
- 2021-02-09 20:48
（sin10＋sin50）/（sin35×sin55）的值详细过程详细
最佳答案
- 五星知识达人网友：低音帝王
- 2021-02-09 21:49
sin10 + sin50
= sin(30-20) + sin(30+20)
= 2 * sin30 * cos20
= cos20
sin35 * sin55
= sin35 * cos35
= 1/2 * sin70
= 1/2 * cos20
∴ (sin10 + sin50) / (sin35 * sin55)
= cos20 / (1/2 * cos20)
= 2
= sin(30-20) + sin(30+20)
= 2 * sin30 * cos20
= cos20
sin35 * sin55
= sin35 * cos35
= 1/2 * sin70
= 1/2 * cos20
∴ (sin10 + sin50) / (sin35 * sin55)
= cos20 / (1/2 * cos20)
= 2
全部回答
- 1楼网友：佘樂
- 2021-02-09 23:14
sin10＋sin50=cos20
sin35·sin55＝ -[cos(35＋55)－cos(35－55)]/2＝ (cos20－cos90)/2＝ cos20/2
（sin10＋sin50）/（sin35×sin55）=2
sin35·sin55＝ -[cos(35＋55)－cos(35－55)]/2＝ (cos20－cos90)/2＝ cos20/2
（sin10＋sin50）/（sin35×sin55）=2
- 2楼网友：患得患失的劫
- 2021-02-09 22:19
sin10 + sin50
= sin(30-20) + sin(30+20)
= 2 * sin30 * cos20
= cos20
sin35 * sin55
=sin35*sin(90-35)
=sin35*cos35
= 1/2 * sin70
= 1/2 * cos20
∴原式= cos20 / (1/2 * cos20)
= 2
= sin(30-20) + sin(30+20)
= 2 * sin30 * cos20
= cos20
sin35 * sin55
=sin35*sin(90-35)
=sin35*cos35
= 1/2 * sin70
= 1/2 * cos20
∴原式= cos20 / (1/2 * cos20)
= 2
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