y=tanx,y(0)=0dy/dx=(secx)^2,则y'(0)=1其二阶导为：y''(x)=2secxsecxtanx,则y''(0)=0其三阶导为：y'''(x)=6(tanx)^2(secx)^2+2(secx)^2=6(secx)^4-4(secx)^2=[6-4(cosx)^2]/(cox)^4=[2+4(sinx)^2]/(cosx)^4所以由公...