21 Formula to project a vector onto a plane 8 Intuition behind the residue at infinity 8 Taking seats on a plane: probability that the last two persons take their proper seats 5 Determine $\lim_{n \to \infty} a_n$ 5 Finding the limit of $\mathop {\lim }\limits_{x \to 0} \frac{x}{{\ln (5x + 1)}}$

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 +20 Finding $\lim_{n\to\infty}\tan{\left(\tan^{-1}{\frac{2}{1^2}}+\tan^{-1}{\frac{2}{2^2}}+...+\tan^{-1}{\frac{2}{n^2}}\right)}$ -2 Are there simple methods for calculating the determinant of symmetric matrices? +10 $f''(x)\leq 0$ implies $f$ concave +10 Formula to project a vector onto a plane

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### Tags (87)

 35 linear-algebra × 12 21 3d 24 calculus × 12 17 functions × 6 23 probability × 17 15 limits × 10 22 real-analysis × 13 13 integration × 8 21 vectors × 2 10 sequences-and-series × 7

### Bookmarks (6)

 74 Integral $\int_1^\infty\frac{\operatorname{arccot}\left(1+\frac{2\pi}{\operatorname{arcoth}x-\operatorname{arccsc}x}\right)}{\sqrt{x^2-1}}\mathrm dx$ 51 Identity for simple 1D random walk 16 Calculate using residues $\int_0^\infty\int_0^\infty{\cos\frac{\pi}2\Big(nx^2-\frac{y^2}n\Big)\cos\pi xy\over\cosh\pi x\cosh\pi y}dxdy,n\in\mathbb{N}$ 13 Unit diameter pentagons with maximum area 3 Geometry Problem For Olympiad