We’re rewarding the question askers & reputations are being recalculated! Read more.

### Questions (45)

 97 All polynomials with no natural roots and integer coefficients such that $\phi(n)|\phi(P(n))$ 24 An information theory inequality which relates to Shannon Entropy 22 Proving $2 ( \cos \frac{4\pi}{19} + \cos \frac{6\pi}{19}+\cos \frac{10\pi}{19} )$ is a root of$\sqrt{ 4+ \sqrt{ 4 + \sqrt{ 4-x}}}=x$ 19 Difference between “Show” and “Prove” 18 Showing $\tan\frac{2\pi}{13}\tan\frac{5\pi}{13}\tan\frac{6\pi}{13}=\sqrt{65+18\sqrt{13}}$

### Reputation (4,566)

This user has no recent positive reputation changes

 27 Alternative proof that $(a^2+b^2)/(ab+1)$ is a square when it's an integer 5 On the factorial equations $A! B! =C!$ and $A!B!C! = D!$ 4 Why does a matrix have determinant zero if one row is the sum of two other rows? 2 Show $f(x)=\sqrt{x^4+1} - \sqrt{x^4+x^2} \rightarrow -1/2$ for $x \rightarrow \infty$, $x \in \mathbb R$. 1 How to answer the question from Calculus by Michael Spivak Chapter 5 Problem 14

### Tags (39)

 32 elementary-number-theory × 16 2 real-analysis 27 square-numbers 1 number-theory × 29 5 factorial 1 calculus 4 matrices × 3 1 limits 4 determinant × 2 0 diophantine-equations × 17