x tan^-1(x^2) dx=arctan(x^2)+x(arctan(x^2))'
=arctan(x^2)+x/(1+x^4)*2x
=arcatn(x^2)+2x^2/(1+x^4)不是太明微分运算法则[u(x)v(x)]'=u'(x)v(x)+u(x)v'(x)x tan^-1(x^2) =(x)'arctan(x^2)+x(arctan(x^2)(tan^-1(x),是反函数的意思，就是arctan)第二步用的是复合函数求导法则