求证1+2sinxcosx/cos^2x-sin^2x=1+tanx/1-tanx

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证明
左=(sin²x+cos²x+2sinxcosx)/[(cosx+sinx)(cosx-sinx)]
=(cosx+sinx)²/[(cosx+sinx)(cosx-sinx)]
=(cosx+sinx)/(cosx-sinx)
分子分母同除没颤袜拦以 cosx
=(1+tanx)/(1-tanx)
得证枯好败

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