Question Number 145602 by mnjuly1970 last updated on 06/Jul/21
$$ \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:…..\mathrm{Advanced}\:………\mathrm{Calculus}….. \\ $$$$\:\:\:\mathrm{Q}::\:\:\:\:\:\:\mathrm{Find}\:\mathrm{the}\:\mathrm{value}\:\mathrm{of}\::: \\ $$$$ \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\begin{array}{|c|c|}{\:{i}\:::\:\:\:\boldsymbol{\phi}\::=\:\int_{\mathrm{0}} ^{\:\mathrm{1}} \mathrm{Ln}\:\left(\:\Gamma\:\left(\:\mathrm{2}\:+\:{x}\:\right)\:\right){dx}\:=\:?\:\:\:\:}\\{\:{ii}\:::\:\:\:\Omega\::=\:\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\:\mathrm{1}}{\:{n}\:\left(\:\mathrm{2}{n}\:+\:\mathrm{3}\:\right)}\:=\:?}\\\hline\end{array} \\ $$$$ \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:…..{m}.{n}.{july}.\mathrm{1970}…..\:\:\:\:\blacksquare \\ $$$$ \\ $$
Answered by ajfour last updated on 06/Jul/21
$$\left({ii}\right) \\ $$$${S}=\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{{n}\left(\mathrm{2}{n}+\mathrm{3}\right)} \\ $$$$\:\:\frac{\mathrm{3}{S}}{\mathrm{2}}=\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\mathrm{2}{n}+\mathrm{3}โ\mathrm{2}{n}}{\mathrm{2}{n}\left(\mathrm{2}{n}+\mathrm{3}\right)} \\ $$$$\:\:\:\:\:\:\:\:=\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\left(\frac{\mathrm{1}}{\mathrm{2}{n}}โ\frac{\mathrm{1}}{\mathrm{2}{n}+\mathrm{3}}\right) \\ $$$$\mathrm{ln}\:\left(\mathrm{1}โ{x}\right)=โ\left({x}+\frac{{x}^{\mathrm{2}} }{\mathrm{2}}+\frac{{x}^{\mathrm{3}} }{\mathrm{3}}+..\right) \\ $$$$\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{\mathrm{2}{n}}=โ\frac{\mathrm{1}}{\mathrm{2}}\underset{{x}\rightarrow\mathrm{1}} {\mathrm{lim}}\:\mathrm{ln}\:\left(\mathrm{1}โ{x}\right) \\ $$$$\mathrm{ln}\:\left(\mathrm{1}+{x}\right)โ\mathrm{ln}\:\left(\mathrm{1}โ{x}\right) \\ $$$$\:\:\:=\mathrm{2}\left({x}+\frac{{x}^{\mathrm{3}} }{\mathrm{3}}+\frac{{x}^{\mathrm{5}} }{\mathrm{5}}+…\right) \\ $$$$\underset{{x}\rightarrow\mathrm{1}} {\mathrm{lim}}\left[\frac{\mathrm{1}}{\mathrm{2}}\left\{\mathrm{ln}\:\left(\mathrm{1}+{x}\right)โ\mathrm{ln}\:\left(\mathrm{1}โ{x}\right)\right\}\right. \\ $$$$\left.\:\:โ{x}โ\frac{{x}^{\mathrm{3}} }{\mathrm{3}}\right]\:=\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{\mathrm{2}{n}+\mathrm{3}} \\ $$$$\frac{\mathrm{3}{S}}{\mathrm{2}}=โ\frac{\mathrm{1}}{\mathrm{2}}\mathrm{lim}\:\mathrm{ln}\:\left(\mathrm{1}โ{x}\right)โ \\ $$$$\underset{{x}\rightarrow\mathrm{1}} {\mathrm{lim}}\left[\frac{\mathrm{1}}{\mathrm{2}}\left\{\mathrm{ln}\:\left(\mathrm{1}+{x}\right)โ\mathrm{ln}\:\left(\mathrm{1}โ{x}\right)\right\}\right. \\ $$$$\left.\:\:\:\:\:\:\:\:\:\:\:\:\:\:โ{x}โ\frac{{x}^{\mathrm{3}} }{\mathrm{3}}\right] \\ $$$$\:\:\frac{\mathrm{3}{S}}{\mathrm{2}}=\:\frac{\mathrm{4}}{\mathrm{3}}โ\frac{\mathrm{ln}\:\mathrm{2}}{\mathrm{2}} \\ $$$$\:\:{S}=\frac{\mathrm{8}}{\mathrm{9}}โ\frac{\mathrm{ln}\:\mathrm{2}}{\mathrm{3}} \\ $$$$\:\:\:\:\:\:\:\:\:\: \\ $$$$\:\:\: \\ $$
Commented by mnjuly1970 last updated on 06/Jul/21
$${bravo}\:{mr}\:{ajfor}\:{your}\:{work}\: \\ $$$$\:{is}\:{admirable}… \\ $$
Answered by Olaf_Thorendsen last updated on 06/Jul/21
$$\Omega\:=\:\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{{n}\left(\mathrm{2}{n}+\mathrm{3}\right)}=\:\frac{\mathrm{1}}{\mathrm{2}}\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{\left({n}+\mathrm{1}\right)\left({n}+\frac{\mathrm{5}}{\mathrm{2}}\right)} \\ $$$$\Omega\:=\:\frac{\mathrm{1}}{\mathrm{2}}.\frac{\psi\left(\frac{\mathrm{5}}{\mathrm{2}}\right)โ\psi\left(\mathrm{1}\right)}{\frac{\mathrm{5}}{\mathrm{2}}โ\mathrm{1}}\:=\:\frac{\mathrm{1}}{\mathrm{3}}\left(\psi\left(\frac{\mathrm{5}}{\mathrm{2}}\right)+\gamma\right) \\ $$$$\psi\left(\frac{\mathrm{5}}{\mathrm{2}}\right)\:=\:\psi\left(\mathrm{1}+\frac{\mathrm{3}}{\mathrm{2}}\right)\:=\:\psi\left(\frac{\mathrm{3}}{\mathrm{2}}\right)+\frac{\mathrm{1}}{\mathrm{3}/\mathrm{2}}\:=\:\psi\left(\frac{\mathrm{3}}{\mathrm{2}}\right)+\frac{\mathrm{2}}{\mathrm{3}} \\ $$$$\psi\left(\frac{\mathrm{3}}{\mathrm{2}}\right)\:=\:\psi\left(\mathrm{1}+\frac{\mathrm{1}}{\mathrm{2}}\right)\:=\:\psi\left(\frac{\mathrm{1}}{\mathrm{2}}\right)+\frac{\mathrm{1}}{\mathrm{1}/\mathrm{2}}\:=\:โ\mathrm{2ln}\left(\mathrm{2}\right)โ\gamma+\mathrm{2} \\ $$$$\: \\ $$$$\Omega\:=\:\frac{\mathrm{1}}{\mathrm{3}}\left(โ\mathrm{2ln}\left(\mathrm{2}\right)โ\gamma+\mathrm{2}+\frac{\mathrm{2}}{\mathrm{3}}+\gamma\right)\:=\:\frac{\mathrm{2}}{\mathrm{3}}\left(\frac{\mathrm{4}}{\mathrm{3}}โ\mathrm{ln}\left(\mathrm{2}\right)\right) \\ $$
Commented by mnjuly1970 last updated on 06/Jul/21
$${grateful}\:{mr}\:{olaf}\: \\ $$$${very}\:{nice}\:{as}\:{always}..{mercey} \\ $$
Answered by qaz last updated on 06/Jul/21
$$\Gamma\left(\mathrm{x}\right)\Gamma\left(\mathrm{1}โ\mathrm{x}\right)=\frac{\pi}{\mathrm{sin}\:\pi\mathrm{x}} \\ $$
Answered by Kamel last updated on 06/Jul/21
$$\left.{i}\right)\:{use}\:{t}=\mathrm{1}โ{x}\:{and}:\:\Gamma\left({t}\right)\Gamma\left(\mathrm{1}โ{t}\right)=\frac{\pi}{{sin}\left(\pi{t}\right)} \\ $$$${ii}..\:\Omega=\underset{{n}=\mathrm{1}} {\overset{+\infty} {\sum}}\frac{\mathrm{1}}{{n}\left(\mathrm{2}{n}+\mathrm{3}\right)}=\frac{\mathrm{2}}{\mathrm{3}}\underset{{n}=\mathrm{1}} {\overset{+\infty} {\sum}}\left(\frac{\mathrm{1}}{\mathrm{2}{n}}โ\frac{\mathrm{1}}{\mathrm{2}{n}+\mathrm{3}}\right)=\frac{\mathrm{2}}{\mathrm{3}}\left(\underset{{n}=\mathrm{1}} {\overset{+\infty} {\sum}}\left(\frac{\mathrm{1}}{\mathrm{2}{n}}โ\frac{\mathrm{1}}{\mathrm{2}{n}+\mathrm{1}}\right)+\underset{{n}=\mathrm{1}} {\overset{+\infty} {\sum}}\left(\frac{\mathrm{1}}{\mathrm{2}{n}+\mathrm{1}}โ\frac{\mathrm{1}}{\mathrm{2}\left({n}+\mathrm{1}\right)+\mathrm{1}}\right)\right) \\ $$$$\:\:\:\:\:\:\:\:\:\:\:=\frac{\mathrm{2}}{\mathrm{3}}\left(\underset{{n}=\mathrm{1}} {\overset{+\infty} {\sum}}\frac{\left(โ\mathrm{1}\right)^{{n}} }{{n}}+\mathrm{1}+\frac{\mathrm{1}}{\mathrm{3}}\right)=\frac{\mathrm{2}}{\mathrm{3}}\left(\frac{\mathrm{4}}{\mathrm{3}}โ{Ln}\left(\mathrm{2}\right)\right)=\frac{\mathrm{8}}{\mathrm{9}}โ\frac{\mathrm{2}{Ln}\left(\mathrm{2}\right)}{\mathrm{3}} \\ $$
Commented by mnjuly1970 last updated on 06/Jul/21
$${tashakor}\:{mr}\:{kamel} \\ $$
Answered by ArielVyny last updated on 06/Jul/21
$$\emptyset=\int_{\mathrm{0}} ^{\mathrm{1}} {ln}\left(\Gamma\left(\mathrm{2}+{x}\right)\right){dx} \\ $$$$=\int_{\mathrm{0}} ^{\mathrm{1}} {ln}\left(\left({x}+\mathrm{1}\right)!\right){dx} \\ $$$${x}+\mathrm{1}={t}\rightarrow{dt}={dx} \\ $$$$\emptyset=\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left({t}!\right){dt}=\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left[\left(\frac{{t}}{{e}}\right)^{{t}} \sqrt{\mathrm{2}\pi{t}}\right] \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left(\frac{{t}}{{e}}\right)^{{t}} +\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left(\sqrt{\mathrm{2}\pi{t}}\right){dt} \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left({e}^{{tln}\left(\frac{{t}}{{e}}\right)} \right)+\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left(\sqrt{\mathrm{2}\pi}\right){dt}+\frac{\mathrm{1}}{\mathrm{2}}\int_{\mathrm{1}} ^{\mathrm{2}} {ln}\left({t}\right){dt} \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left(\frac{{t}}{{e}}\right)+{ln}\left(\sqrt{\mathrm{2}\pi}\right)+\frac{\mathrm{1}}{\mathrm{2}}\left[{xln}\left({x}\right)โ{x}\right]_{\mathrm{1}} ^{\mathrm{2}} \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left({t}\right)โ\int_{\mathrm{1}} ^{\mathrm{2}} {tdt}+{ln}\left(\sqrt{\mathrm{2}\pi}\right)+\frac{\mathrm{1}}{\mathrm{2}}\left(\mathrm{2}{ln}\left(\mathrm{2}\right)+\mathrm{1}\right) \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left({t}\right){dt}โ\frac{\mathrm{3}}{\mathrm{2}}+\frac{\mathrm{1}}{\mathrm{2}}{ln}\left(\mathrm{2}\pi\right)+\frac{\mathrm{2}{ln}\mathrm{2}}{\mathrm{2}}+\frac{\mathrm{1}}{\mathrm{2}} \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left({t}\right){dt} \\ $$$${du}={ln}\left({t}\right)\:\:\:\:\:\:\:\:\:\:\:\:\:\:{v}={t} \\ $$$${u}={tln}\left({t}\right)โ{t}\:\:\:\:\:\:\:\:\:{dv}=\mathrm{1} \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left({t}\right)=\left[{t}^{\mathrm{2}} {ln}\left({t}\right)โ{t}\right]โ\int{tlntdt}+\int{tdt} \\ $$$$\mathrm{2}\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left({t}\right){dt}=\left[{t}^{\mathrm{2}} {ln}\left({t}\right)โ{t}+\frac{\mathrm{1}}{\mathrm{2}}{t}^{\mathrm{2}} \right]_{\mathrm{1}} ^{\mathrm{2}} =\mathrm{4}{ln}\left(\mathrm{2}\right)โ\mathrm{2}+\frac{\mathrm{1}}{\mathrm{2}}\mathrm{4}+\mathrm{1}โ\frac{\mathrm{1}}{\mathrm{2}} \\ $$$$\int_{\mathrm{1}} ^{\mathrm{2}} {tln}\left({t}\right){dt}=\mathrm{2}{ln}\left(\mathrm{2}\right)โ\mathrm{1}+\mathrm{1}+\frac{\mathrm{1}}{\mathrm{2}}โ\frac{\mathrm{1}}{\mathrm{4}} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:=\mathrm{2}{ln}\left(\mathrm{2}\right)+\frac{\mathrm{1}}{\mathrm{4}} \\ $$$$\emptyset=\mathrm{2}{ln}\left(\mathrm{2}\right)+\frac{\mathrm{1}}{\mathrm{4}}โ\frac{\mathrm{3}}{\mathrm{2}}+\frac{{ln}\left(\mathrm{2}\pi\right)}{\mathrm{2}}+\frac{\mathrm{2}{ln}\left(\mathrm{2}\right)}{\mathrm{2}}+\frac{\mathrm{1}}{\mathrm{2}} \\ $$$$\emptyset=\mathrm{2}{ln}\left(\mathrm{2}\right)+\frac{\mathrm{1}}{\mathrm{4}}โ\mathrm{1}+\frac{{ln}\left(\mathrm{8}\pi\right)}{\mathrm{2}} \\ $$$$\emptyset=โ\frac{\mathrm{3}}{\mathrm{4}}+\frac{\mathrm{2}{ln}\left(\mathrm{4}\right)}{\mathrm{2}}+\frac{{ln}\left(\mathrm{8}\pi\right)}{\mathrm{2}} \\ $$$$\emptyset=โ\frac{\mathrm{3}}{\mathrm{4}}+\frac{\mathrm{1}}{\mathrm{2}}{ln}\left(\mathrm{8}^{\mathrm{3}} \pi\right) \\ $$
Commented by mathmax by abdo last updated on 06/Jul/21
$$\mathrm{t}!\sim\left(\frac{\mathrm{t}}{\mathrm{e}}\right)^{\mathrm{t}} \sqrt{\mathrm{2}\pi\mathrm{t}}\mathrm{is}\:\mathrm{valable}\:\mathrm{pour}\:\mathrm{t}\:\mathrm{assez}\:\mathrm{grand}\left(\mathrm{t}\rightarrow\infty\right) \\ $$