Mathematics
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crskhr

Our true needs are deeper – yet in our modern society most of us reflexively and relentlessly pursue wealth, consumer goods and admiration. We have learned from Perelman's mathematics. Perhaps we should also pause to reflect on ourselves and learn from Perelman's attitude towards life. : Bill Thurston

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20 Can the group $\mathbb Z \times \mathbb Z$ be written as union of finitely many proper subgroups of it? Sep 26 '19
15 How does one evaluate $\int \frac{\sin(x)}{\sin(5x)} \ dx$ Oct 19 '14
15 Prove: $\sin (\tan x) \geq {x}$ Jan 18 '14
14 How to show $\sum_{k=0}^{n}\binom{n+k}{k}\frac{1}{2^k}=2^{n}$ Jul 29 '16
13 If $f(1)=1$, then is it true that $f(n)=n$ for all $n \in \mathbb{N}\cup\{0\}$. Oct 4 '17
12 Find the value of: $\sum_{n=1}^{50}n(n!)$ May 1 '15
11 Is $\left( {{2}^{x}}-1 \right)\left( {{5}^{x}}-1 \right)$ a square number for integer $x>1$ Jul 24 '18
9 Alternating sum of binomial coefficients multiplied by (1/k+1) Oct 8 '14
8 Sum of $50$ terms of $\cot^{-1}3+\cot^{-1}7+\cot^{-1}13+\cot^{-1}21+…$ Dec 15 '18
8 How to calculate $\lim_{x\to0} \frac{\ln(1+x)+\ln(1-x)}{x^2}$? Nov 1 '17
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