New posts in Proof Explanation

How do we know that the Sine function has no Non-Real Roots?

Milnor's exercise: for any manifold $M$, $\mathrm{Hom}(C^\infty(M,\mathbb{R}),\mathbb{R})\cong M$

Sieve of Eratosthenes : why can we stop at the $\sqrt n$?

Understand part of a proof to show that if K is normal in G, then K is the kernel of a homomorphism

How to understand an example in Krattenthaler's “Advanced Determinant Calculus”?

Proof of $\lim_{n \to \infty}(1+\frac{1}{n})^n=e$

Trouble with the proof of Cauchy convergence criterion

Calculating $\phi(100)$ where $\phi$ is the totient function

Let $f(n) = an^2 + bn + c$ be a quadratic function. Show that there's an $n ∈ N$ such that $f(n)$ is not a prime number.

When does equality hold in $\Bigr\lvert\sum_{k=1}^n a_kb_k\Bigr\rvert^2 \le \left(\sum_{k=1}^n |a_k|^2\right)\left(\sum_{k=1}^n |b_k|^2\right)$?