解析
2cos(sin-cos)
=2cosxsinx-2cos^2x
=sin2x-2cos^2x
=sin2x-(cos2x+1)
=sin2x-cos2x-1
=√2sin(2x-π/4）-1第三步不明白因为2cos^x-1=cos2x 所以2cos^2=cos2x+1明白了不谢，答题不易，请谅解，满意请采纳，谢谢