kuch nahi
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### Questions (78)

 46 How to understand and appreciate the prime number industry? 26 Math behind rotation in MS Paint 21 Do other non-native english speakers have trouble solving certain kinds of problems? 18 Evaluate $\sum\limits_{k=1}^n k^2$ and $\sum\limits_{k=1}^n k(k+1)$ combinatorially 17 Can I ever go wrong if I keep thinking of derivatives as ratios?

### Reputation (2,924)

 +5 If $f(xy)=f(x)f(y)$ then show that $f(x) = x^t$ for some t +5 Can I ever go wrong if I keep thinking of derivatives as ratios? +5 What is the reason for these jiggles when truncating infinite series? +5 Why is closure omitted in some group definitions?

 29 Results that were widely believed to be false but were later shown to be true 8 How to calculate $\int \sqrt{(\cos{x})^2-a^2} \, dx$ 7 How to do this approximation? 7 What could be an intuitive explanation for $\sum\limits_{k=1}^{\infty}\frac{1}{k2^k} = \log 2$? 7 Prove that $\sum\limits_{k=1}^nk^2 = \frac{n(n+1)(2n+1)}{6}$?

### Tags (73)

 13 combinatorics × 20 8 discrete-mathematics × 2 13 calculus × 11 8 elliptic-functions 10 sequences-and-series × 6 8 indefinite-integrals 10 approximation × 3 7 summation × 2 8 limits × 5 6 radicals

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