Cute problem: determinant of $I_n+(f_if_j)

probability of guessing a k-digit number sequentially from n trials

Does every number divide some $n^2+1$?

How do I prove this trigonometry inequality $\sin^2(y) \leq 2 \sin^2(x) + 2\sin^2(y-x)$?

Vector norm of integral inequality

prove if f is continuous and $\lim\limits _{x\to\infty}f\left(x\right)=L\neq0$ then $\int\limits _{1}^{\infty}f\left(x\right)\sin x\,dx$ diverges

Number of roots of the equation $f(xf(x)) = \sqrt{9 - x^2f^2(x)}$

If $f$ is uniformly continuous on the dense set $E \subset X$ then a continuous extension of $f$ exists on $X$.

Construction of symmedians but different.

Is there a positive integer $n$ such that the prime divisors of $n^3 - 1$ are $2$, $3$ and $7$?

A surjective homomorphism which is not an isomorphism for rings (Using basic algebra)

What is $\lim_{x \to \infty} \frac{\sin x}{\sin x}?$

"Drawing a Picture" of $\operatorname{Spec}(\mathbb{Z})$

Cute problem: determinant of $I_n+(f_if_j)_{i,j}$