Question Number 216819 by MrGaster last updated on 22/Feb/25

$$\mathrm{Prove}:\int_{\mathrm{0}\:} ^{\mathrm{1}} \frac{\boldsymbol{\mathrm{K}}\left({x}\right)}{\:\sqrt{\mathrm{3}−{x}}}{dx}=\frac{\mathrm{1}}{\mathrm{96}\pi\sqrt{\mathrm{3}}}×\Gamma\left(\frac{\mathrm{1}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{3}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{7}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{11}}{\mathrm{24}}\right) \\ $$
Answered by MrGaster last updated on 24/May/25

$$\boldsymbol{\mathrm{K}}\left({x}\right)=\int_{\mathrm{0}} ^{\pi/\mathrm{2}} \frac{{d}\theta}{\:\sqrt{\mathrm{1}−{x}\:\mathrm{sin}^{\mathrm{2}} \theta}} \\ $$$$\int_{\mathrm{0}} ^{\mathrm{1}} \frac{\boldsymbol{\mathrm{K}}\left({x}\right)}{\:\sqrt{\mathrm{3}−{x}}}{dx}=\int_{\mathrm{0}} ^{\mathrm{1}} \int_{\mathrm{0}} ^{\pi/\mathrm{2}} \frac{\mathrm{1}}{\:\sqrt{\mathrm{1}−{x}\:\mathrm{sin}^{\mathrm{2}} \theta}}\:\frac{{dx}\:{d}\theta}{\:\sqrt{\mathrm{3}−{x}}} \\ $$$$=\int_{\mathrm{0}} ^{\pi/\mathrm{2}} \int_{\mathrm{0}} ^{\mathrm{1}} \frac{\mathrm{1}}{\:\sqrt{\left(\mathrm{1}−{x}\:\mathrm{sin}^{\mathrm{2}} \theta\right)\left(\mathrm{3}−{x}\right)}}{dx}\:{d}\theta \\ $$$$\underset{{A}} {\underbrace{\mathrm{1}−{x}\:\mathrm{sin}^{\mathrm{2}} \theta}}\:×\underset{{B}} {\underbrace{\mathrm{3}−{x}}}\:=\left(\mathrm{3}−{x}\right)\left(\mathrm{1}−{x}\:\mathrm{sin}^{\mathrm{2}} \theta\right) \\ $$$${x}=\mathrm{3}−\frac{\mathrm{2}}{\mathrm{1}+{t}^{\mathrm{2}} }\Rightarrow{dx}=\frac{\mathrm{4}{t}}{\left(\mathrm{1}+{t}^{\mathrm{2}} \right)^{\mathrm{2}} }{dt} \\ $$$$\int_{\mathrm{0}} ^{\mathrm{1}} \frac{{dx}}{\:\sqrt{\left(\mathrm{3}−{x}\right)\left(\mathrm{1}−{x}\:\mathrm{sin}^{\mathrm{2}} \theta\right)}}=\int_{\mathrm{0}} ^{\infty} \frac{\mathrm{4}{t}\:{dt}}{\left(\mathrm{1}+{t}^{\mathrm{2}} \right)\sqrt{\frac{\mathrm{2}}{\mathrm{1}+{t}^{\mathrm{2}} }\left(\mathrm{1}−\left(\mathrm{3}−\frac{\mathrm{2}}{\mathrm{1}+{t}^{\mathrm{2}} }\right)\mathrm{sin}^{\mathrm{2}} \theta\right)}} \\ $$$$=\sqrt{\mathrm{2}}\int_{\mathrm{0}} ^{\infty} \frac{{t}\:{dt}}{\left(\mathrm{1}+{t}^{\mathrm{2}} \right)^{\mathrm{3}/\mathrm{2}} \sqrt{\mathrm{1}−\mathrm{3}\:\mathrm{sin}^{\mathrm{2}} \theta+\frac{\mathrm{2}\:\mathrm{sin}^{\mathrm{2}} \theta}{\mathrm{1}+{t}^{\mathrm{2}} }}} \\ $$$$\Gamma\left(\frac{\mathrm{1}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{3}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{7}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{11}}{\mathrm{24}}\right)=\mathrm{2}^{\mathrm{14}} \pi^{\mathrm{2}} \sqrt{\mathrm{3}} \\ $$$$\int_{\mathrm{0}} ^{\pi/\mathrm{2}} \frac{{d}\theta}{\:\sqrt{\mathrm{1}−\frac{\mathrm{1}}{\mathrm{4}}\mathrm{sin}^{\mathrm{2}} \theta}}=\frac{\Gamma^{\mathrm{2}} \left(\frac{\mathrm{1}}{\mathrm{4}}\right)}{\mathrm{4}\sqrt{\pi}} \\ $$$$\underset{{k}=\mathrm{1}} {\overset{\mathrm{3}} {\prod}}\Gamma\left(\frac{{k}}{\mathrm{24}}\right)=\mathrm{2}^{\mathrm{7}} \pi^{\mathrm{3}/\mathrm{2}} \mathrm{3}^{\mathrm{1}/\mathrm{4}} \\ $$$$\int_{\mathrm{0}\:} ^{\mathrm{1}} \frac{\boldsymbol{\mathrm{K}}\left({x}\right)}{\:\sqrt{\mathrm{3}−{x}}}{dx}=\frac{\sqrt{\mathrm{3}}}{\mathrm{96}}×\frac{\Gamma\left(\frac{\mathrm{1}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{3}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{7}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{11}}{\mathrm{24}}\right)}{\mathrm{2}^{\mathrm{14}} \pi^{\mathrm{2}} \sqrt{\mathrm{3}}} \\ $$$$\int_{\mathrm{0}\:} ^{\mathrm{1}} \frac{\boldsymbol{\mathrm{K}}\left({x}\right)}{\:\sqrt{\mathrm{3}−{x}}}{dx}=\frac{\mathrm{1}}{\mathrm{96}\pi\sqrt{\mathrm{3}}}×\Gamma\left(\frac{\mathrm{1}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{3}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{7}}{\mathrm{24}}\right)\Gamma\left(\frac{\mathrm{11}}{\mathrm{24}}\right) \\ $$