let's focus on good definitions...” Today, I'll explore a seemingly simple question: what is a rotation? I'm asking for the definition of a rotation, which »

Pierre de Fermat (1607-1665) is my outlier of mathematics: not because math was just a hobby for him — he was a lawyer by profession; nor »

Sorry for the long hold up on another post. This new post is a result on my investigations on a proof of $$\zeta(2) = \frac{\pi^ » Today, I'll prove Euler's Pentagonal Number Theorem and show how he used it to find recurrence formulae for the sum of \(n$$'s positive divisors and »