求值:sin35°cos25°+sin55°cos65°
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解决时间 2021-02-11 14:10
- 提问者网友:半生酒醒
- 2021-02-10 19:26
求值:sin35°cos25°+sin55°cos65°
最佳答案
- 五星知识达人网友:零点过十分
- 2021-02-10 20:20
若a+b=90°,则sina=cosb
Cos(a-b)=cosacosb+sinasinb
sin35°cos25°+sin55°cos65°
=sin35°sin65°+cos35°cos65°
=cos(65°-35°)
=cos30°=√3/2
Cos(a-b)=cosacosb+sinasinb
sin35°cos25°+sin55°cos65°
=sin35°sin65°+cos35°cos65°
=cos(65°-35°)
=cos30°=√3/2
全部回答
- 1楼网友:往事隔山水
- 2021-02-10 22:40
sin35°cos25°+sin55°cos65°
=sin35°cos25°+cos35°sin25°
=sin(35°+25°)
=sin60°
=√3/2
=sin35°cos25°+cos35°sin25°
=sin(35°+25°)
=sin60°
=√3/2
- 2楼网友:慢性怪人
- 2021-02-10 21:48
sin35°cos25°=cos55sin65
sin35°cos25°+sin55°cos65°=cos55sin65 + sin55°cos65
=sin(55+65)
=sin120
=sin60
sin35°cos25°+sin55°cos65°=cos55sin65 + sin55°cos65
=sin(55+65)
=sin120
=sin60
- 3楼网友:归鹤鸣
- 2021-02-10 20:53
sin55=cos35,cos65=sin25,原式=sin35cos25+cos35sin25=sin60。。。
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