f(x)=cos²(nπ+x)sin²(nπ-x)/cos²[(2n+1)π-x]=cos²(x)sin²(x)/cos²(x)=sin²(x)∴f(π/2010)+f(502π/1005)=sin²(π/2010)+sin²(502π/1005)=[1-cos(π/2010)]/2+[1-...=[1-cos(π/2010)]/2+[1-cos(1004π/1005)]/2这一步中除以2是什么意思公式：cos2a=cos²a-sin²a=1-2sin²a∴sin²a=(1-cos2a)/2 改一下=[1-cos(π/1005)]/2+[1-cos(1004π/1005)]/2