y"
=[e^arctanx*(x^2+1)/(x^2+1)+e^arctanx*2x]/(x^2+1)^2
=e^arctanx*(1+2x)/(x^2+1)^2
y"=0得到x=-1/2
在x<-1/2時y"<0,函數y為凸函數
在x>-1/2時y">0,函數y為凹函數
x=-1/2時y=e^[-arctan(1/2)]
凸區間為(-無窮,-1/2)
凹區間為(-1/2,+無窮)
拐點(-1/2,e^[-arctan(1/2)])