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12h
revised Straight Edge - Only Geometric Construction
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12h
answered Straight Edge - Only Geometric Construction
13h
comment An integral related with the Riemann $\zeta$ function
@Dr.MV: that is a nice shortcut, thank you, Mark.
13h
revised Is $ \sum\limits_{n=1}^\infty \frac{|\sin n|^n}n$ convergent?
added 34 characters in body
13h
revised An integral related with the Riemann $\zeta$ function
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13h
revised An integral related with the Riemann $\zeta$ function
edited tags; edited title
13h
answered An integral related with the Riemann $\zeta$ function
15h
reviewed Edit Prove that $\tan20^\circ\tan40^\circ\tan60^\circ\tan80^\circ=3$
15h
revised Prove that $\tan20^\circ\tan40^\circ\tan60^\circ\tan80^\circ=3$
I changed 60^{0} into 60^{\circ} to eliminate possible confusion.
16h
answered Determine wether $\sum_{n=1}^\infty \frac{3n-1}{(n+1)^3}$ converges or diverges.
16h
answered Is there closed form of integral of gamma function with specific range
1d
accepted A nice and hard colouring problem
1d
awarded  Nice Answer
1d
awarded  Nice Answer
2d
awarded  Nice Answer
2d
comment Tridiagonal band matrix, finding its inverse norm
See identity $(19)$ here: mathworld.wolfram.com/ChebyshevPolynomialoftheSecondKind.html. The eigenvalues of your matrix are not difficult to find.
2d
comment Is $f(x)=\sum_{n\geq 1}\frac{(-x)^n}{n^2+1}$ convex at $x=0$?
It is a convex function for every $x\in(-1,1)$.
2d
revised Is $f(x)=\sum_{n\geq 1}\frac{(-x)^n}{n^2+1}$ convex at $x=0$?
added 295 characters in body
2d
comment Is $f(x)=\sum_{n\geq 1}\frac{(-x)^n}{n^2+1}$ convex at $x=0$?
We may say even more than convexity holds in a neighbourhood of zero. Such a function is convex on the whole interval of convergence $[-1,1]$.
2d
revised Is $f(x)=\sum_{n\geq 1}\frac{(-x)^n}{n^2+1}$ convex at $x=0$?
edited title