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Prove-0-1-2-arcsin-2-x-x-dx-pii-6-pi-2-36-Li-2-1-i-3-2-1-3-3-




Question Number 222858 by MrGaster last updated on 09/Jul/25
Prove:  ∫_0 ^(1/2) ((arcsin^2 x)/x)dx=((πi)/6)((π^2 /(36))−Li_2 (((1+i(√3))/2)))−(1/3)ζ(3)
$$\mathrm{Prove}: \\ $$$$\int_{\mathrm{0}} ^{\frac{\mathrm{1}}{\mathrm{2}}} \frac{\mathrm{arcsin}^{\mathrm{2}} {x}}{{x}}{dx}=\frac{\pi{i}}{\mathrm{6}}\left(\frac{\pi^{\mathrm{2}} }{\mathrm{36}}−\mathrm{Li}_{\mathrm{2}} \left(\frac{\mathrm{1}+{i}\sqrt{\mathrm{3}}}{\mathrm{2}}\right)\right)−\frac{\mathrm{1}}{\mathrm{3}}\zeta\left(\mathrm{3}\right) \\ $$
Commented by gabthemathguy25 last updated on 09/Jul/25
wait im still answering sir.
$$\mathrm{wait}\:\mathrm{im}\:\mathrm{still}\:\mathrm{answering}\:\mathrm{sir}. \\ $$
Answered by gabthemathguy25 last updated on 10/Jul/25
∫_0 ^(1/2) ((arcsin^2 x)/x)dx = (1/2)∫_0 ^(π/3) (t^2 /(sin t))dt  ⇒((πi)/2)((π^2 /(18))−Li_2 (e^(i(π/3)) ))−ζ(3)  e^(i(π/3)) =cos((π/3))+isin((π/3))=(1/2)+i((√3)/2)=(1/2)(1+i(√3))  ⇒((πi)/2)((π^2 /(18))−Li_2 ((1/2)(1+i(√3))))−ζ(3)  ⇒((πi)/6)((π^2 /(36))−Li_2 (((1+i(√3))/2)))−(1/3)ζ(3) :)
$$\int_{\mathrm{0}} ^{\frac{\mathrm{1}}{\mathrm{2}}} \frac{\mathrm{arcsin}^{\mathrm{2}} {x}}{{x}}{dx}\:=\:\frac{\mathrm{1}}{\mathrm{2}}\int_{\mathrm{0}} ^{\frac{\pi}{\mathrm{3}}} \frac{{t}^{\mathrm{2}} }{\mathrm{sin}\:{t}}{dt} \\ $$$$\Rightarrow\frac{\pi{i}}{\mathrm{2}}\left(\frac{\pi^{\mathrm{2}} }{\mathrm{18}}−\mathrm{Li}_{\mathrm{2}} \left({e}^{{i}\frac{\pi}{\mathrm{3}}} \right)\right)−\zeta\left(\mathrm{3}\right) \\ $$$${e}^{{i}\frac{\pi}{\mathrm{3}}} =\mathrm{cos}\left(\frac{\pi}{\mathrm{3}}\right)+{i}\mathrm{sin}\left(\frac{\pi}{\mathrm{3}}\right)=\frac{\mathrm{1}}{\mathrm{2}}+{i}\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}=\frac{\mathrm{1}}{\mathrm{2}}\left(\mathrm{1}+{i}\sqrt{\mathrm{3}}\right) \\ $$$$\Rightarrow\frac{\pi{i}}{\mathrm{2}}\left(\frac{\pi^{\mathrm{2}} }{\mathrm{18}}−\mathrm{Li}_{\mathrm{2}} \left(\frac{\mathrm{1}}{\mathrm{2}}\left(\mathrm{1}+{i}\sqrt{\mathrm{3}}\right)\right)\right)−\zeta\left(\mathrm{3}\right) \\ $$$$\left.\Rightarrow\frac{\pi{i}}{\mathrm{6}}\left(\frac{\pi^{\mathrm{2}} }{\mathrm{36}}−\mathrm{Li}_{\mathrm{2}} \left(\frac{\mathrm{1}+{i}\sqrt{\mathrm{3}}}{\mathrm{2}}\right)\right)−\frac{\mathrm{1}}{\mathrm{3}}\zeta\left(\mathrm{3}\right)\::\right) \\ $$

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