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 2d answered Symmetric Matrix Equation Nov 26 answered Relationship between Nullspaces Nov 13 comment Computing the integral of a differential form in $\mathbb{R}^{2}$. I think it would be easier to use polar coordinates $(r,\theta)$. Oct 27 comment Einstein manifolds and topology Yes. It really depends on your definition of Einstein manifold. You can define Einstein manifold to satisfy $Ric=kg$ for some constant $k$. Or you can define Einstein manifold to satisfy $Ric=\frac{R}{n}g$, or equivalently, the traceless Einstein tensor is zero. But they are equivalent by the Bianchi identity, at least for $n\geq 3$. Oct 27 answered Einstein manifolds and topology Oct 18 reviewed Close Sum of finite series involving square roots Oct 17 reviewed Approve Coefficient to create a series whose sum is a given one Oct 16 awarded Popular Question Oct 16 answered Why $\Delta f-|\nabla f|^2 =0$ ,$f$ is a function on compact manifold. Oct 13 reviewed Looks OK Find all primes $p$ and $q$ such that $p^2-2q^2=1.$ Oct 13 reviewed Close Number the conjugacy classes of a group of odd order is also is odd. Oct 10 answered Particular solution of $y'' +9y' +20y = e^{-4t}$? Oct 10 reviewed Reviewed An easy reference for genetic algorithm Oct 9 reviewed Approve Wrong Solution to Geometric Brownian Equation Oct 9 reviewed Close What is the difference between regular expression $(x + y)^*$ and $(x^*y^*)$? Oct 1 revised Evaluate the sum $\sum_1^n{2k+1\over k(k+1)}$ in closed form added 3 characters in body; edited title Sep 29 comment $g(x) = x^2f(x)$, how to prove $g'(x) = x^2 f'(x) + 2x f(x)$ Or use product rule: en.wikipedia.org/wiki/Product_rule Sep 28 reviewed Looks OK Absolute value of hyperbolic function Sep 28 answered Is the series $\sum 5^n/(4^n+3)$ convergent or not? Sep 28 reviewed No Action Needed Vectors with constant angle between any two of them.