$M^{2\times 2}(\mathbb{Z})$ has identity $e_1$, but a certain subring $R$ has another identity $e_2$ and $e_1 \notin R$.
Ring and Subring with different Identities
Scamming a scammer? I have seen many questions like:      My question is: what happens if you receive this money (without doing anything or giving your bank account number) but do not do anything scammer wants?  I especially want to know about what happens with the money you got and possible legal consequences.    Is it considered yours because scammer transfered it to you? Do you have to return it? If yes, to whom and in what form? And finally, how is it that scammers are just sending money to random people? Aren't they scared that someone will simply not return it? I understand that this may be stolen money, but it surely took some effort (cash/time) to "acquire" it, so why are they just sending it away? Sorry if this is the wrong place to ask this, I'm new to the site :/  My issue is this: when editing in vim, my syntax file highlights underscores and carets when found in non-math text, which is fine, except vim doesn't recognize that "align" is a math environment. What do I need to do to fix this? So a buddy and I were playing a game of Magic that turned out to be a really quick game because he got  out on the battlefield early. He was tapping it without attacking because of its obviously awesome ability but I don't know if you can tap a creature for its Inspired (untap-triggered) ability without attacking for it to then be tapped. Are you allowed to tap a creature whenever you want? Using HTML5/Canvas/JavaScript to take in-browser screenshots Differences in the behaviour of pinching a garden hose and closing a tap Let's say you have a garden hose connected to an ordinary water tap which is opened fully. If you pinch the end of the hose, water leaves the hose at a higher speed (and this can be useful while watering plants, to reach pots which are further away). However when a tap (with no hose connected) is opened only slightly, water flows out at a low speed, possibly even in drops.  The actions of pinching the end of a hose and of almost-closing an open tap seem similar, so why the difference in behaviour? How to show that there is an element of order $51$ in the multiplicative group $(Z/103Z)^∗.$  I can't use Cauchy's theorem since $51$ is not prime. Peer to Peer: Methods of Finding Peers Are there any known methods of finding peers without using a dedicated central server?  ie: If I have peers which are disconnecting and reconnecting to the internet but getting a new IP address each time, and I want to connect to them without setting up a dedicated server to register with.  I was thinking about using peers email address to send a manifest of connected peers periodically, with some sort of timecode, negating the need for a dedicated server.  This would be a fallback if none of the peers could be connected to after trying all the previously known peer addresses.  But existing models of finding peers would be preferable. I understand that if a particle approaches a finite potential barrier of height $V_0$ with energy $E &lt; V_0$, there is still a finite probability of finding the particle on the other side of the barrier due to quantum tunneling.  My question is, since the wavefunction is nonzero inside the barrier region, is it possible to actually make a position measurement and locate a particle inside the barrier?  I mean, if we can say that "there is a nonzero probability that the particle is inside the barrier", surely this would suggest we can do so?  If not, why not? Am I understanding the whole wavefunction/probability distribution thing right? How do I get started creating an Ubuntu Desktop App? I don't always answer myself, but when I do, I fail to ask a good question Sometimes I'll encounter problems while coding, or sometimes out of simple interest for a question, I'll google for an answer, and most of the time I find that answer is here on stackoverflow.com.   If I can't find an answer, or if it's not enough to satisfy my curiosity, sometimes I expend my own effort to solve those questions. And after I've solved it, I'm happy to make my contribution to the community, and I post them as the Q&amp;A style posts. For example:     It seems relatively easier to ask a question if I didn't already have a solution, and I can put what I have so far in the question body, such as:     The problem to me is, if I have my own solution to my own question, then most of what I have so far becomes part of the solution. It's likely I have failed in making my contribution by asking a question to which I have an answer, for example:     So I'm wondering if there are some guidelines or good practices for Q&amp;A style posts?   How do I do it better? Example of a group where $o(a)$ and $o(b)$ are finite but $o(ab)$ is infinite Let G be a group and $a,b \in G$. It is given that $o(a)$ and $o(b)$ are finite. Can you give an example of a group where $o(ab)$ is infinite? Tag links in tag excerpts not shown properly If a tag excerpt contains a link to another tag with the [tag:foobar] syntax, this link is not properly shown in every context. For an example see . The link is shown as [tag:school-libraries] but it should be  or at least "school-libraries". Correct usage for "all you need is/are..." Killing thread after some specified time limit in Java Please tell me is there any fundamental difference between the two sentences:   Even today, people continue to use cheques.  Even today, people are continuing to use cheques.    I mean is there a difference as in time period (i.e when the action starts and when it ends). Or are the two sentence just the same and interchangeable? My random variable $X$ is normally distributed with mean $b$ and variance $p$. I defined a new RV, $Y$, such that $Y=1/X$. Does anyone know how to find the mean of $Y$ and $Y^2$? Toggle Switch to swap the connections of two buttons I am trying to mod my arcade stick so I can switch two commonly swapped buttons on the controller.  Essentially they are simple 2 terminal momentary switches connected directly to the controller PCB. I would like to switch their responsibilities, so in my case the Back button and the LB button on the XBox pcb I would like to swap so the Back actuates the LB button on the PCB and the LB actuates the Back button.  My assumption is that I would need a switch with 8 terminals, 4 in 4 out.  What type of switch am I looking for? I'm trying to include graphics in my Latex-file, which I compiled with latex+dvipdf on OS X. Latex however returns this error: "Cannot determine size of graphic"  My graphic is exported from PowerPoint, so I have tried both .pdf and .png. I get the same errors for both.  Sample code that doesn't work:  \begin{figure}[htb] \begin{center} \leavevmode \includegraphics[width=0.8\textwidth]{graph.png} \end{center} \end{figure}   If I have to manually set some measurements of the image, please tell me how I can find out those measurements. I need the image to take up about 80% of text width and be centered. Thanks. Laptop battery charge management I work on a HP laptop plugged in most of the time, and after a few months the battery went off-duty.  Of course, I could remove the battery each time the laptop is plugged and replace it each time I must move to where no sockets are around. But I think that:   It would be really BORING! The computer would not avail itself of the useful backup power supply a battery can provide in case of black out.   It should simply switch off the battery charging when a safe power level is reached (i.e. 95%) and start recharging it, not every five minutes, but only under a certain safe threshold (i.e. 40% - 50%).  In its energy-saving profiles, Windows 7 only allows for setting up screen brightness, screen fadeout, screen deactivation and the suspension, not managing any charging issue.  Is there a way to accomplish this? I would like to ask for some simple examples showing the uses of &lt;div&gt; and &lt;span&gt;.   I've seen them both used to mark a section of a page with an id or class, but I'm interested in knowing if there are times when one is preferred over the other.