x→0时,直接代入就可以得出cos2x/cosx＝1你吧整个2cos2xsinx / 2sin4xcosx化简过程给写一下吧~谢谢啦没问题2cos2xsinx / 2sin4xcosx＝cos2xsinx / (sin4xcosx)=cos2xsinx / (2sin2xcos2xcosx)=sinx / (2sin2xcosx)=sinx / (4sinxcos^2x)=1/(4cos^2x)