Question Number 74446 by rajesh4661kumar@gmail.com last updated on 24/Nov/19
Answered by Kunal12588 last updated on 24/Nov/19
$${I}=\int{e}^{{tan}^{−\mathrm{1}} {x}} \left(\frac{\mathrm{1}+{x}+{x}^{\mathrm{2}} }{\mathrm{1}+{x}^{\mathrm{2}} }\right){dx} \\ $$$${let}\:{t}={tan}^{−\mathrm{1}} {x} \\ $$$$\Rightarrow{dt}=\frac{{dx}}{\mathrm{1}+{x}^{\mathrm{2}} } \\ $$$${I}=\int{e}^{{t}} \left(\mathrm{1}+{tan}\:{t}\:+\:{tan}^{\mathrm{2}} \:{t}\right){dt} \\ $$$$\Rightarrow{I}=\int{e}^{{t}} \left({tan}\:{t}\:+\:{sec}^{\mathrm{2}} \:{t}\right){dt}\:\:\circledast \\ $$$$\Rightarrow{I}={e}^{{t}} {tan}\:{t}\:+{C} \\ $$$$\Rightarrow{I}={xe}^{{tan}^{−\mathrm{1}} {x}} \:+{C} \\ $$$$\circledast\:\int{e}^{{x}} \left[{f}\left({x}\right)+{f}\:'\left({x}\right)\right]{dx}={e}^{{x}} {f}\left({x}\right)+{C} \\ $$
Commented by Kunal12588 last updated on 24/Nov/19
$$\int{e}^{{x}} \left[{f}\left({x}\right)+{f}\:'\left({x}\right)\right]{dx} \\ $$$$=\int{e}^{{x}} {f}\left({x}\right){dx}+\int{e}^{{x}} {f}\:'\left({x}\right)\:{dx} \\ $$$$={e}^{{x}} {f}\left({x}\right)−\int{e}^{{x}} {f}\:'\left({x}\right){dx}+\int{e}^{{x}} {f}\:'\left({x}\right){dx} \\ $$$$={e}^{{x}} {f}\left({x}\right)+{C} \\ $$