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ln-e-x-1-e-x-1-dx-




Question Number 87769 by john santu last updated on 06/Apr/20
∫ ((ln(e^x +1))/(e^(−x) +1)) dx
$$\int\:\frac{\mathrm{ln}\left(\mathrm{e}^{\mathrm{x}} +\mathrm{1}\right)}{\mathrm{e}^{−\mathrm{x}} +\mathrm{1}}\:\mathrm{dx}\: \\ $$
Answered by TANMAY PANACEA. last updated on 06/Apr/20
∫((e^x ln(e^x +1))/(e^x +1))dx  t=ln(e^x +1)→(dt/dx)=(e^x /(e^x +1))  ∫tdt=(t^2 /2)+c  (({ln(e^x +1)}^2 )/2)+c
$$\int\frac{{e}^{{x}} {ln}\left({e}^{{x}} +\mathrm{1}\right)}{{e}^{{x}} +\mathrm{1}}{dx} \\ $$$${t}={ln}\left({e}^{{x}} +\mathrm{1}\right)\rightarrow\frac{{dt}}{{dx}}=\frac{{e}^{{x}} }{{e}^{{x}} +\mathrm{1}} \\ $$$$\int{tdt}=\frac{{t}^{\mathrm{2}} }{\mathrm{2}}+{c} \\ $$$$\frac{\left\{{ln}\left({e}^{{x}} +\mathrm{1}\right)\right\}^{\mathrm{2}} }{\mathrm{2}}+{c} \\ $$
Answered by john santu last updated on 06/Apr/20

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