求证 1-tanα÷1+tanα=1-2sinαcosα÷cosα²-sinα求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sin求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sinα
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![求证 1-tanα÷1+tanα=1-2sinαcosα÷cosα²-sinα求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sin求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sinα](/uploads/image/z/1241553-57-3.jpg?t=%E6%B1%82%E8%AF%81+1-tan%CE%B1%C3%B71%2Btan%CE%B1%3D1-2sin%CE%B1cos%CE%B1%C3%B7cos%CE%B1%26%23178%3B-sin%CE%B1%E6%B1%82%E8%AF%81+1-tan%CE%B1%C3%B71%2Btan%CE%B1%3D1-2sin%CE%B1cos%CE%B1%C3%B7cos%26%23178%3B-sin%E6%B1%82%E8%AF%81+1-tan%CE%B1%C3%B71%2Btan%CE%B1%3D1-2sin%CE%B1cos%CE%B1%C3%B7cos%26%23178%3B-sin%CE%B1)
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求证 1-tanα÷1+tanα=1-2sinαcosα÷cosα²-sinα求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sin求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sinα
求证 1-tanα÷1+tanα=1-2sinαcosα÷cosα²-sinα
求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sin求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sinα
求证 1-tanα÷1+tanα=1-2sinαcosα÷cosα²-sinα求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sin求证 1-tanα÷1+tanα=1-2sinαcosα÷cos²-sinα
右边
=(sin²a+cos²a-2sinacosa)/(cosa+sina)(cosa-sina)
=(cosa-sina)²/(cosa+sina)(cosa-sina)
=(cosa-sina)/(cosa+sina)
山下除以cosa
由sina/cosa=tana
所以=(1-tana)/(1+tana)=右边
命题得证