Question

求求下列函数的二阶导数,急用,

Answer 1

y'=arctanx+x/(1+x^2)

y"=1/(1+x^2)+[1+x^2-x*2x]/(1+x^2)^2

=1/(1+x^2)+(1-x^2)/(1+x^2)^2

=2/(1+x^2)^2