已知tana=3, (1)sina-cosa/sina+cosa (2)(sina)^2-3sinacosa+1 急!

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已知tana=3, (1)sina-cosa/sina+cosa (2)(sina)^2-3sinacosa+1 急!
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已知tana=3, (1)sina-cosa/sina+cosa (2)(sina)^2-3sinacosa+1 急!
已知tana=3, (1)sina-cosa/sina+cosa (2)(sina)^2-3sinacosa+1 急!

已知tana=3, (1)sina-cosa/sina+cosa (2)(sina)^2-3sinacosa+1 急!
1、(sina-cosa)/(sina+cosa )=(tana-1)/(tana+1)
=(3-1)/(3+1)=1/2.(cosa≠0)
2、原式=(cosa)^2*[(tana)^2-3tana]+1
=(cosa)^2[3^2-3*3)+1
=1.(cxosa≠0)