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证明sin^4x-cos^4x=sin^2x-cos^2x
人气:212 ℃ 时间:2020-06-14 10:15:13
解答
sin^4x-cos^4x=(sin^2x-cos^2x )(sin^2x+cos^2x)
=(sin^2x-cos^2x )*1=(sin^2x-cos^2x )
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