sin^6x+cos^6x=(sin^2x+cos^2x)(sin^4x-sin^2xcos^2x+cos^4x)=sin^4x-sin^2xcos^2x+cos^4x=(sin^2x+cos^2x)^2-3sin^2xcos^2x=1-3sin^2xcos^2x所以分子=3sin^2xcos^2xsin^4x+cos^4x=(sin^2x+cos^2x)^2-2sin^2xcos^2x=...