狂野歌
春芽
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原式=sin^8X-2sin^4xcos^4X+cos^8X+4sin^2Xcos^2x
=(sin^4x-cos^4x)^2+4sin^2Xcos^2x
=[(sin^2x-cos^2x)(sin^2x+cos^2x)]^2+4sin^2Xcos^2x
=(sin^2x-cos^2x)^2+4sin^2Xcos^2x
=sin^4x-2sin^2Xcos^2x+cos^4x+4sin^2Xcos^2x
=sin^4x+2sin^2Xcos^2x+cos^4x
=(sin^2x+cos^2x)^2
=1
1年前
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