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已知sin阿法=3/5,阿法属于(派/2,派),tan(派-被打)=1/2,求tan(阿法-2贝打)的值
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已知sin阿法=3/5,阿法属于(派/2,派),tan (派-被打)=1/2,求tan (阿法-2贝打)的值
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答案和解析
sina=3/5
cosa=-4/5
tana=-3/4
tan(π-b)=-tanb=1/2
tanb=-1/2
tan2b=2tanb/(1-tan^2b)=-1/3
tan(a-2b)=(tana-tan2b)/(1+tanatan2b)=(-3/4+1/3)/(1+1/4)
=-1/3
cosa=-4/5
tana=-3/4
tan(π-b)=-tanb=1/2
tanb=-1/2
tan2b=2tanb/(1-tan^2b)=-1/3
tan(a-2b)=(tana-tan2b)/(1+tanatan2b)=(-3/4+1/3)/(1+1/4)
=-1/3
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