How can I go about drawing a colored box around a column in a matrix with an arrow and text like this:    Here is the code that I have thus far:  \documentclass[11pt]{book}  \usepackage{amsmath,amsfonts,amssymb,amsthm}  \makeatletter \renewcommand*\env@matrix[1][*\c@MaxMatrixCols c]{%   \hskip -\arraycolsep   \let\@ifnextchar\new@ifnextchar   \array{#1}} \makeatother  \usepackage{tikz}   \begin{document}  \begin{equation} \begin{bmatrix}[cccc|c]   1 &amp; 0 &amp; -1 &amp; 0 &amp; 0 \\   0 &amp; 1 &amp; 2 &amp; 0 &amp; 0 \\   0 &amp; 0 &amp; 0 &amp; 1 &amp; 0 \end{bmatrix}\\ \end{equation}  \end{document}
I have a matrix and need to highlight some elements in the matrix. I have found how to highlight a single element (I want to put the cell in the square):  $$ A = \begin{bmatrix} \fbox{0} &amp; \fbox{0} &amp; 0 \\  \fbox{0} &amp; \fbox{0} &amp; 0 \\ 1 &amp; 1 &amp; 1 \\  \end{bmatrix}$$   But how can I outline elements of the submatrix like in the picture below? I need just a frame where some elements are located.
Some conditions require that a person lie in bed all the time until recovered. Is there a name for such conditions or people experiencing them at the moment?   For example,      I am currently &lt;bed sick&gt; and can't help you with your homework.   I tried looking for bed sick but hit a dead end. How can wifi penetrate through walls when visible light can't? I did search the question on Physics S.E considering it would be previously asked. I found this  But in this question , the answers are w.r.t to or in comparison with microwaves , their absorption and certain other things. I didn't find a sort of general answer that could be the answer to the question. So the question is - wifi or radio waves  reach us through concrete walls . They also reach us through the ceiling (if some one is using it in the flat above ours ). Even through the air they travel such a lot , bending around corners or doors . Now I would not compare them to microwaves (because I don't want the answer in terms of properties of the material but physics). Visible light which is so much powerful than them can't penetrate black opaque paper leave alone the walls. Same is true for gamma rays (penetration through a very thick wall). So why then radio waves being so very less powerful than light  waves are able to travel through walls? There should be a general concept as to why the radio waves are able to pass through walls but microwaves or light waves cannot ! A linked question is also that sound travels much faster in solids(walls) but is not audible in it though it is in air. After reading @BillN's answer, it would be really helpful if any one could explain it in terms molecular resonance or crystalline structure or electrical conductivity or how does molecular resonance or crystalline structure or electrical conductivity cause this. Shiny locked Legendaries in ORAS Serebii says that (probably) the only  in ORAS are Kyogre, Groudon, Rayquaza and Deoxys. This means that Reshiram and Zekrom, that were shiny locked in BW/B2W2, now can be found shiny.    Can anyone prove this? I'd like to know if it's true before waste hours in softresetting. Say if I have a dropdown in a form and I have another nested class inside of this class . Now what's the best way to access this dropdown from the nested class? The square of an integer is congruent to 0 or 1 mod 4 This is a question from the free Harvard online abstract algebra .  I'm posting my solutions here to get some feedback on them.  For a fuller explanation, see  post.  This problem is from assignment 6.  The notes from this lecture can be found .     a) Prove that the square $a^2$ of an integer $a$ is congruent to 0 or 1 modulo 4.   b) What are the possible values of $a^2$ modulo 8?   a) Let $a$ be an integer. Then $a=4q+r, 0\leq r&lt;4$ with $\bar{a}=\bar{r}$.  Then we have $a^2=a\cdot a=(4q+r)^2=16q^2+8qr+r^2=4(4q^2+2qr)+r^2, 0\leq r^2&lt;4$ with $\bar{a^2}=\bar{r^2}$.  So then the possible values for $r$ with $r^2&lt;4$ are 0,1.  Then $\bar{a^2}=\bar{0}$ or $\bar{1}$.  b) Let $a$ be an integer. Then $a=8q+r, 0\leq r&lt;8$ with $\bar{a}=\bar{r}$.  Then we have $a^2=a\cdot a=(8q+r)^2=64q^2+16qr+r^2=8(8q^2+2qr)+r^2, 0\leq r^2&lt;8$ with $\bar{a^2}=\bar{r^2}$.  So then the possible values for $r$ with $r^2&lt;8$ are 0,1,and 2.  Then $\bar{a^2}=\bar{0}$, $\bar{1}$ or $\bar{4}$.  Again, I welcome any critique of my reasoning and/or my style as well as alternative solutions to the problem.  Thanks. How is the popularity of "recent tags" calculated? How are these calculated? I see them going up and down all the time, and there are obviously way more than 48 questions about C# so how are these calculated? Is infinite regress of causation possible? Is infinite regress of causation necessary? For a number of reasons &mdash; including perhaps a desire to feel that we have a complete understanding of where we came from, or at least an understanding which is completely sufficient for all of our purposes &mdash; there is a strong tendency to suppose that an infinite regress of causes and effects is impossible. We see this for instance in the . Traditionally in Greco-Roman influenced philosophy, this prime mover has been identified with the notion of a creator god. A more modern formulation comes from the Big Bang theory, which (although we study the question) happened for no reason that we know of; and perhaps occurred for no reason at all. Indeed, if time is a property of the universe, a good argument can be made that .  At the same time, we have gotten a lot of leverage in science from the ideas that everything happens for a reason, i.e.&nbsp;because it is caused by something else. This is sometimes described as the . Aristotle also applies this idea, except that the first mover is made an exception, something which exists literally for no reason. Indeed, the emotionally negative way that "no reason" is used in common speech, as something groundless and irrational, indicates how widespread the feeling is that the idea of uncaused events is deeply dissatisfying.  Almost all of our modes of critical thinking are infused with both of these ideas: that we may work from first principles, a definite starting point, counting up from zero (or one, historically); but also that we may trace the causes of things to some point, and then later ask how that starting point came to be. But the two ideas are themselves in conflict.  Which is true &mdash; that infinite causal chains are impossible? Or that they are necessary? Or are they perhaps possible without being necessary?   Related questions: I am not sure if  works. Can someone please help me? My phone is new and in its warranty period so I can't root it yet. I tried this app but I am not sure if it actually did something. Unlike the other famous app on the PlayStore for fstrim, it doesn't require root access which is quite incredible. What is the best way to remove and prevent leaf stains on concrete pavers? apt-get update fails to fetch files, “Temporary failure resolving …” error Err http://archive.canonical.com natty InRelease     Err http://security.ubuntu.com oneiric-security InRelease                Err http://extras.ubuntu.com natty InRelease                             Err http://security.ubuntu.com oneiric-security Release.gpg   Temporary failure resolving ‘security.ubuntu.com’ Err http://archive.canonical.com natty Release.gpg   Temporary failure resolving ‘archive.canonical.com’ Err http://extras.ubuntu.com natty Release.gpg   Temporary failure resolving ‘extras.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric InRelease Err http://gb.archive.ubuntu.com oneiric-updates InRelease Err http://gb.archive.ubuntu.com natty-backports InRelease Err http://gb.archive.ubuntu.com oneiric Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric-updates Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com natty-backports Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’  Reading package lists... Done W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/InRelease       W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/InRelease   W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/InRelease   W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘archive.canonical.com’ W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/Release.gpg  Temporary failure resolving ‘security.ubuntu.com’ W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘extras.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Some index files failed to download. They have been ignored, or old ones used instead.   This is what I'm seeing when I try to run sudo apt-get update. I did an update on my instance yesterday and am now experiencing this. How to convert a HEIF/HEIC image to JPEG in El Capitan? So, here’s the thing. I have a new iPhone and an old Mac. iOS 11 (still in beta as of today) and El Capitan (no more updates for this Mac). I use iCloud photo library in both devices. When I take a photo in the new format with my iPhone 7, is there any way to use it right away in my mac, without having to convert it in my iPhone first? I mean, can I get those photos synced through iCloud and converted locally on my Mac?  I have tried to find a third party software that could do that kind of conversion, but was not able to find any that would work on El Capitan. Any idea? Convince grep to output all lines, not just those with matches In chrome, most of the time, when i middle click on a link (text or image), it opens a new tab and the current tab does not change. This is the expected behaviour.  However, some websites have links (i'd say 5%) that also switches the current tab to the new one. For example: on this , the name of the players in the main list have the problem.  By looking at the source, i didn't find anything anormal (the link is a standard html tag). But if i disable javascript, i have not the problem. I looked at the source, and didn't find the problematic script... Note also that if i open the tab with right click > open link in new tab, there is no problem.  I'd like to know if you find the reason of the problem and how i can fix it. I am running chrome 10.0.648.204 on windows 7 x64.  EDIT: the website above does not exhibit the behavior anymore, but I sill have the problem sometimes on other sites (which I don't remember) How do I access folders created on Ubuntu with Windows? I have an external hard drive on which I back up my files, and I've moved some files from an Ubuntu laptop to it as well. However, I can't find a way to open the folder containing these files with my main Windows 10 laptop. When I try to open the folder "VPC 3 : UBUNTU" (the "VPC" is just a name for the laptop  with no special implications), the following happens:  It responds with "___ is unavailable. Make sure the disk is inserted..." Did Stephen Baxter or Arthur C. Clarke's estate ever comment on continuing "A Time Odyssey"? 2007 book "Firstborn", the third and last book of "" trilogy by Stephen Baxter and Arthur C. Clarke - an "orthoquel" to "2001: A Space Odyssey" - ends with a cliffhanger which obviously implies continuation:      Myra said, “My God.Charlie? ”  Bisesa stared. “Who is ‘we’?”  “We call ourselves the Lastborn. We are at war. We are losing.” She held out her hands. “Please. Come with me now.”  Bisesa and Myra, still hugging each other, reached out their free hands. Their fingertips touched Charlie’s.  A clash of cymbals.   However, sadly, Sir Arthur died in 2008, with no further books forthcoming.  Did Stephen Baxter  or Arthur C. Clarke's estate ever comment on continuing "A Time Odyssey" after 2008?  Wikipedia has no info:     The 2008 Gollancz edition of the most recent book describes itself on the cover as the "Conclusion" of the series, but the plot is not concluded in the book. The immediate threat is averted but the enemy is not defeated, suggesting that further novels in the series were intended. With the death of Clarke, one of the two authors, it is not clear whether these will be written. You may have encountered a situation in which Mac changes the order of desktops based on some events like alerts on a program or a web page in browser. How could I disable this logical change? Note: I'm using El Capitan, but I had this problem since Mavericks. In addition to showing reputation scores, SO should rank users. In the users section, users are ordered by the reputations they have.  Each user should also have a unique rank, since many users can have the same reputation score.  Rank must follow the order laid out by reputation, but for those having similar reputation, an additional formula should be defined which can rank users based on tags, time since registration, frequency of activity and/or helpfulness of their answers.  What are your thoughts on this? What is the size of this microcontroller? Having trouble reading a data sheet Repeating “will” for two verbs with “and” Constructing the reciprocal of a segment How can one construct the reciprocal length of a line segment? For example, given any line segment a, how can $\frac{1}{a}$ be constructed?  I was told that it can be solved by creating similar triangles, but I do not get it.