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已知sinx+cosx=根号2求下列各式的值 sin^4x-cos^4x
人气:468 ℃ 时间:2019-08-20 03:15:03
解答
sinx+cosx=√2
(sinx+cosx)^2=2
sin2x=1
cos2x=0
sin^4x-cos^4x
=(sin^2x+cos^2x)(sin^2x-cos^2x)
=(sin^2x-cos^2x)
=-cos2x
原式=-cos2x=0
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