let [imath]t = e^x \implies dt = e^x \, dx \implies dx = \dfrac{dt}{t}[/imath]
[imath]\displaystyle \int \dfrac{\arctan{t}}{t^3} \, dt[/imath]
[imath]u = \arctan{t} \implies du = \dfrac{dt}{1+t^2}[/imath]
[imath]dv = \dfrac{dt}{t^3} \implies v = -\dfrac{1}{2t^2}[/imath]
[imath]\displaystyle \int u \, dv = u \cdot v - \int v \, du[/imath]
proceed with the above integration by parts as recommended by the Banana. Note that another iteration of integration by parts for the (v du) integral may be needed.