求证tan^2x+1/tan^2x=[2(3+cos4x)]/(1-cos4x)

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求证tan^2x+1/tan^2x=[2(3+cos4x)]/(1-cos4x)
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求证tan^2x+1/tan^2x=[2(3+cos4x)]/(1-cos4x)
求证tan^2x+1/tan^2x=[2(3+cos4x)]/(1-cos4x)

求证tan^2x+1/tan^2x=[2(3+cos4x)]/(1-cos4x)
左边=sin^2x/cos^2 + cos^2/sin^2x=(sin^4x+cos^4x)/(cos^2xsin^2x)=(sin^2x+cos^2x)^2-2sin^2xcos^2x/(sin^2xcos^2x)=(1-sin^2(2x)/2)/(sin^2(2x)/4)=[4-2(1-cos4x)/2]/[(1-cos4x)/2]=右边