必修二,三角函数已知2tanA=3tanB求证tan(A-B)=sin2B/5-cos2B

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必修二,三角函数已知2tanA=3tanB求证tan(A-B)=sin2B/5-cos2B

必修二,三角函数已知2tanA=3tanB求证tan(A-B)=sin2B/5-cos2B
必修二,三角函数
已知2tanA=3tanB求证tan(A-B)=sin2B/5-cos2B

必修二,三角函数已知2tanA=3tanB求证tan(A-B)=sin2B/5-cos2B
tan(A-B)=(tanA-tanB)/(1+tanAtanB)=tanB/(2+3tanBtanB)
=sinBcosB/(2cosBcosB+3sinBsinB)
=sin2B/(6-2cos2Bcos2B)
=sin2B/(5-cos2B)