tana+1/tana=3,求sina*cosa tan^2 a+1/tan^2 a

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tana+1/tana=3,求sina*cosa tan^2 a+1/tan^2 a
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tana+1/tana=3,求sina*cosa tan^2 a+1/tan^2 a
tana+1/tana=3,求sina*cosa tan^2 a+1/tan^2 a

tana+1/tana=3,求sina*cosa tan^2 a+1/tan^2 a
tana+1/tana=3可化成sina/cosa+cosa/sina=3 化简 得sin^2a+cos^2a /sinacosa=3可得出
sinacosa=1/3 由此可得出 sina+cosa=根号15/3 cosa-sina=根号3/3
sina*cosa tan^2 a+1/tan^2 a=sina*cosa (1-cos^2a +sin^2a/1+cos^2a-sin^2a)+(1+cos^2a-sin^2a/1-cos^2a+sin^2a)
因为cos^2a -sin^2a=(sina+cosa)(cosa-sina) 将式子代入上式
得出的就是答案14+3倍根号5/3