y=arctanx求导y'=1/(1+x^2)=1-x^2+x^4-x^6+...积分还原:y=x-x^3/3+x^5/5-x^7/7+....因此有:arctanx^2=x^2-x^6/3+x^10/5-x^14/7+....(arctanx^2)/x=x-x^5/3+x^9/5-x^13/7+....-(-1)^nx^(4n-3)/(2n-1)+..