化简sin(540°-x)/tan(900°-x)•{1/[tan(450°-x)tan(810°-x)]}R

化简sin(540°-x)/tan(900°-x)•{1/[tan(450°-x)tan(810°-x)]}•{cos(360°-x)/[sin(-x)]}
【正确答案】：原式=[sin(180°-x)/tan(-x)]•{1/[tan(90°-x)tan(90°-x)]}•[cosx/sin(-x)]=(sinx/-tanx)•tanx•tanx[-(1/tanx)=sinx．