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 Apr 14 accepted Find minimum of $a+b$ under the condition $\frac{m^2}{a^2}+\frac{n^2}{b^2}=1$ where $m,n$ are fixed arguments Apr 14 asked Find minimum of $a+b$ under the condition $\frac{m^2}{a^2}+\frac{n^2}{b^2}=1$ where $m,n$ are fixed arguments Apr 3 asked Estimate the bound of the sum of the roots of $1/x+\ln x=a$ where $a>1$ Apr 3 awarded Notable Question Feb 12 accepted $1+xy+yz+xz-x-y-z>0$ where $x,y,z \in (0,1)$ Feb 11 asked $1+xy+yz+xz-x-y-z>0$ where $x,y,z \in (0,1)$ Dec 22 accepted Diagonalizable transmit to submatrix Dec 18 asked Diagonalizable transmit to submatrix Dec 8 asked Estimate $\sum_{\left|\frac{k}{n}-x\right|>\delta}\binom nk x^k(1-x)^{n-k}$ Dec 3 accepted If a separately continuous function $f : [0,1]^2 \to \mathbb{R}$ vanishes on a dense set, must it vanish on the whole set? Dec 1 asked If a separately continuous function $f : [0,1]^2 \to \mathbb{R}$ vanishes on a dense set, must it vanish on the whole set? Nov 26 accepted Find $\lim (a_{n+1}^\alpha-a_n^\alpha)$ Nov 21 revised The continuous relationship between $f(x,y)$ and $\varphi(x)=\lim f(x,y)$ edited tags Nov 21 asked The continuous relationship between $f(x,y)$ and $\varphi(x)=\lim f(x,y)$ Nov 20 comment Show $\sum_{n=1}^\infty \frac 1n\,\sin\left(\Bigl(n-\frac 12\Bigr)\pi+\frac xn\right)$ converges uniformly and continuously differentiable. I think $\sum f_n$ converges uniformly is not use M test. When $n > a$, then $\cos(x/n)/n$ is $\rightarrow 0$ monotonously. Then use Leibniz Test. Nov 20 comment Show that the derivative of a function is not continuous $g'(x)=\begin{cases} 1+4x\sin\frac{1}{x}-2\cos\frac{1}{x}&\text{ if }x\neq0\\\ 1&\text{ if }x=0 \end{cases}$ $g'(\frac{1}{2n\pi})<0$, $g'(\frac{1}{2n\pi+\pi/2})>0$,By intermediate value theorem \$\exists \frac{1}{2n\pi+\pi/2}