JetXO.com!~ Flight4me.com!~ LineXO.com!~ Free Insights and Airline. Australia and Oceania. ÐÕÐÐ¡ÐÐÐÐÐÐÐÐÐÐÐÐ¦ÐÐÐÐÐÐ! ~ Frank PowerQ: Why is $\{0\}\times\{0\}$ a closed subset of $\mathbb{R}^2$? Wikipedia says If we set $X = \{(x, y)\ |\ x^2 + y^2 0$ be arbitrary and choose $r$ such that $r > \sqrt{x_0^2 + y_0^2}$. Since $r^2 \sqrt{x_0^2+y_0^2}$ because $r>x_0$ and $r>y_0$, as $x_0^2+y_0^2\leq(x_0-r)^2+(y_0-r)^2$. Q: Changing the endpoint location of a Key in a user’s keys folder I recently decided to back up a number of user’s keys for one of my servers. I used the command rake seahub:restore_keys and it seemed to work fine but out of curiosity, I wanted to see what the keys that were restored would actually