## π Day puzzle for 3/14

Happy π Day. The goal of this question is to calculate the area for a circle of radius 3, where A = πr². The catch is that you have to use the constant π that is defined in a different language ...

## Why doesn't /etc/fstab use xml or json?

This is more like a general Linux / programming question but I've been programming for a while and I'm used to using a format such as XML/JSON on any file which is used for config purposes. Being a …

## Join lists of lists with unique id

Sorry for the vague title, but I can't describe my problem properly and shortly. I am maintaining a list of players and their games with the following form: gamesPerPlayer = {{playerId -> ...

## TikZ - Recursive Arc Drawing

I'm trying to make Farey diagrams similar to those seen here (click) or the screenshot as follows, Namely, I'd like an example of the one seen on the top of page 6. From there I hope I can figure …

## 4, 8, 15, 16, 23, 42

4, 8, 15, 16, 23, 42 Write a program that outputs this sequence of numbers infinitely. However, The Numbers may not appear in your source code anywhere. The following is not a valid Java program to …

## Will shaving my head decrease my chances of employment?

What do employers usually think about bald employees? I'm thinking about shaving my head because I have recently been converted to Buddhism, but if it will significantly hurt my chances at getting a …

## How can Diablo appear in Diablo III when his soulstone was destroyed in Diablo II?

I still don't understand this part. In Diablo II Diablo's soulstone is destroyed preventing his return forever but at the end of Diablo III we face him once again. How is this possible?

## Would Gandalf have been promoted to the white if he had not fought the Balrog?

Gandalf was promoted to a White wizard after his body was destroyed in the battle with the Balrog. This was done mainly to replace Saruman as he had joined Sauron (or at least swayed significantly …

## Trolling the troll

A troll has captured you and is forcing you to write malware (defined as a program that damages the computer that runs it). The troll can read and understand code, but is not so good at spotting bugs. …

## How can I determine whether a student has written an excellent paper themselves, or hired someone else to do it?

In class, over the course of a semester, I tend to build up a mental model of individual students' communication abilities. For example, one student might seem more or less eloquent than another when …

## What is the optimal algorithm for the game 2048?

I have recently stumbled upon the game 2048. You need to merge similar tiles by moving them in any of the four directions. Similarly, I mean tiles with the same value. After each move, a new tile ...

## What should a GM do about players using magic in unforeseen, breaking ways?

Firstly, a quick anecdote. In our most recent Pathfinder session our cleric jokingly mentioned he will soon be able to summon 1d3 dolphins. Another player then mentioned that some dolphins (orca) can …

## Analogues of P vs. NP in the history of mathematics

Recently I wrote a blog post entitled "The Scientific Case for P≠NP". The argument I tried to articulate there is that there seems to be an "invisible electric fence" separating the problems in P …

## Why don't all motors burn up instantly?

A motor rated for 3S (11.1V) has an internal resistance of 0.12 Ohm. The max. current is 22A. 11.1V / 0.12 Ohm = 92.5A Doesn't this mean that by supplying a 11.1V three phase current, the motor ...

## A coworker rejected my romantic advances and I got her fired, how do I recover from this?

So this was a while back, when I was working as a Project Coordinator (I've been promoted now), a new PC joined our team and it was my job to train her. I was attracted to her and we talked and ...

## Why does exclamation mark within double quotes cause a Bash error?

If anyone wants to close as dupe of Differences between doublequotes " ", singlequotes ' ' and backticks ´ ´ on commandline? please leave a comment explaining how answers …

## Error 000368 selectbylocation in script

When i trying to do Select by location i got : arcgisscripting.ExecuteError: Failed to execute. Parameters are not valid. ERROR 000368: Invalid input data. Failed to execute (SelectLayerByLocation) I …

## Indian Rupee Symbol

On OS X, Shift-Option-2 prints the Euro symbol €. Is there a shortcut to print the Indian Rupee Symbol ₹?

## How to draw a corner at the end of text

I would like to draw my logo with latex. The logo is very simple. It is a text, followed by a corner, which started at the bottom line. The size of the corner should change according to the font …

We are given the series $\sum_{n=1}^\infty {\frac {f(n)} {n(n+1)}}$, where $f(n)$ is such a function that it equals to the sum of 1's in the binary representation of n. I'm obliged to find the sum of …
## What does periodicity of $e^{-iHt/\hbar}$ mean in physical terms?
The unitary time evolution operator $U(t)=e^{-iHt/\hbar}$ has some distinct flavour of periodicity to it because of $e^{x+2\pi i}=e^x$. Is this periodicity reflected in any way in physical systems? …