... advanced calculus...
prove that : Σ_(n=1) ^∞ (1/(n^2 (((2n)),(n) ))) =^(???) ((ζ(2))/3)
solution:: Σ_(n=1) ^∞ (1/(n^2 ∗(((2n)!)/((n!)^2 ))))=Σ_(n=1) ^∞ ((n!∗n!)/(n^2 ∗(2n)!))
=Σ_(n=1) ^∞ ((Γ(n)Γ(n+1))/(nΓ(2n+1)))=Σ_(n=1) ^∞ ((β(n,n+1))/n)
=Σ_(n=1) ^∞ (1/n)∫_0 ^( 1) x^(n−1) (1−x)^n
=∫_0 ^( 1) (1/x)Σ(((x−x^2 )^n )/n)dx
=−∫_0 ^( 1) ((ln(1−x+x^2 ))/x)dx
=−∫_0 ^( 1) ((ln(1+x^3 )−ln(1+x))/x)dx
=∫_0 ^( 1) ((ln(1+x))/x)dx −∫_0 ^( 1) ((ln(1+x^3 ))/x)dx
=−li_2 (−1) −∫_0 ^( 1) ((Σ_(n=1) (((−1)^(n+1) x^(3n) )/n))/x) dx
=(π^2 /(12))+Σ_(n=1) ^∞ (((−1)^n )/n)∫_0 ^( 1) x^(3n−1) dx
=(π^2 /(12)) +(1/3)Σ_(n=1) ^∞ (((−1)^n )/n^2 ) =(π^2 /(12))−(π^2 /(36))
=(π^2 /(18)) =((ζ(2))/3) ✓✓
m.n.july.1970..
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