Question Number 222848 by MrGaster last updated on 09/Jul/25 | ||
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$$ \\ $$$$\int_{\mathrm{0}} ^{\mathrm{1}} \frac{\mathrm{arcatn}^{\mathrm{2}} {x}}{{x}}{dx}=\frac{\pi}{\mathrm{2}}{G}−\frac{\mathrm{7}}{\mathrm{8}}\zeta\left(\mathrm{3}\right) \\ $$ | ||
Answered by MrGaster last updated on 09/Jul/25 | ||
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$$\mathrm{cos}\:{x}=\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\mathrm{sin}\left(\mathrm{2}{n}+\mathrm{1}\right){x} \\ $$$${I}=\int_{\mathrm{0}} ^{\mathrm{arctan}} \frac{{x}^{\mathrm{2}} }{\mathrm{tan}\:{x}}=\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{4}}} \frac{{x}^{\mathrm{2}} }{\mathrm{tan}{x}}\mathrm{sec}^{\mathrm{2}} {xdx}=\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{4}}} \frac{{x}^{\mathrm{2}} }{\mathrm{sin}{x}\mathrm{cos}{x}}{dx} \\ $$$$=\mathrm{2}\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{4}}} \frac{{x}^{\mathrm{2}} }{\mathrm{sin}{x}}{dx}=\mathrm{2}\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{4}}} \frac{\left({x}/\mathrm{2}\right)^{\mathrm{2}} }{\mathrm{sin}{x}}{dx}/\mathrm{2}=\frac{\mathrm{1}}{\mathrm{4}}\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{2}}} \frac{{x}^{\mathrm{2}} }{\mathrm{sin}{x}}{dx},{G}=\mathrm{0}.\mathrm{915965594177219} \\ $$$$=\frac{\mathrm{1}}{\mathrm{4}}\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{2}}} {x}^{\mathrm{2}} \mathrm{2}\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\mathrm{sin}\left(\mathrm{2}{n}+\mathrm{1}\right){xdx}=\frac{\mathrm{1}}{\mathrm{2}}\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{2}}} {x}^{\mathrm{2}} \mathrm{sin}\left(\mathrm{2}{n}+\mathrm{1}\right){xdx} \\ $$$$=\frac{\mathrm{1}}{\mathrm{2}}\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\left[\frac{\pi\left(−\mathrm{1}\right)^{{n}} }{\left(\mathrm{2}{n}−\mathrm{1}\right)^{\mathrm{2}} }−\frac{\mathrm{2}}{\left(\mathrm{2}{n}+\mathrm{1}\right)^{\mathrm{3}} }\right]=\frac{\pi}{\mathrm{2}}\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\frac{\left(−\mathrm{1}\right)^{{n}} }{\left(\mathrm{2}{n}−\mathrm{1}\right)^{\mathrm{2}} }−\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{\left(\mathrm{2}{n}+\mathrm{1}\right)^{\mathrm{3}} } \\ $$$$=\frac{\pi}{\mathrm{2}}{G}−\frac{\mathrm{7}}{\mathrm{8}}\zeta\left(\mathrm{3}\right) \\ $$ | ||