Jean-Sébastien
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 Oct13 revised Coupon selecting problem added 1024 characters in body Oct13 answered Coupon selecting problem Oct12 comment Another math contest problem: $\int_0^{\frac{\ln^22}4}\,\frac{\arccos\frac{\exp\sqrt x}{\sqrt2}}{1-\exp\sqrt{4\,x}}dx$ @VladimirReshetnikov makes more sense now. I was only saying that because $1>\ln^2(2)/4.$ Oct12 comment Another math contest problem: $\int_0^{\frac{\ln^22}4}\,\frac{\arccos\frac{\exp\sqrt x}{\sqrt2}}{1-\exp\sqrt{4\,x}}dx$ Is that $\ln(2)^ 2/4$ in the upper bound? Oct12 reviewed Approve real analysis functions and interval Oct11 reviewed Looks OK How to prove this assertion in $S_n$ for $n \geq 3$? Oct11 reviewed No Action Needed How to find area of triangle from its medians Oct11 reviewed Approve Find a plane that passes through a point and is parallel to a given plane Oct11 reviewed Approve Why is the area under a curve the integral? Oct10 comment Is a rational-valued continuous function $f\colon[0,1]\to\mathbb{R}$ constant? @copper.hat I meant the intermediate value theorem. I somehow always confuse the name of these Oct10 comment Is a rational-valued continuous function $f\colon[0,1]\to\mathbb{R}$ constant? @DanielFischer True enough! Oct10 comment Is a rational-valued continuous function $f\colon[0,1]\to\mathbb{R}$ constant? @DanielFischer with the mean value theorem, one could use density to prove it must pass through some irrational Oct10 reviewed Approve About $e^{\pi}\gt {\pi}^e, \ e^{e^{\pi}}\lt {\pi}^{{\pi}^{e}},e^{{\pi}^{{\pi}^e}}\gt {\pi}^{e^{e^{\pi}}}$ and their generalization Oct10 comment Finding the value of ${\mathop{\sum\sum\sum\sum}_{0\le i\lt j\lt k\lt l\le n }} \,n$ Since $0$ is included, that would be ${n+1}\choose 4$. Oct7 comment Can you help me with a limit? I formatted your question. Make sure I've done it correctly Oct7 revised Can you help me with a limit? Format, grammar and retagged Oct6 comment How can we directly see that the number of random walks starting and ending at the origin is ${n\choose n/2}^2$? @IanMateus I've changed it quite a bit, I think the problem in my last one was that I forgot to consider the walks that were made of say more NS than EW. Oct6 revised How can we directly see that the number of random walks starting and ending at the origin is ${n\choose n/2}^2$? added 220 characters in body Oct5 answered How can we directly see that the number of random walks starting and ending at the origin is ${n\choose n/2}^2$? Oct5 reviewed Approve General Exponential modular equation