When we look at parallel rail tracks, it appears to converge at a certain angle. Let us say the width of the tracks is d and the height of the eye is h. Assuming one stands in the middle of the tracks, what is the angle at which the tracks appear to converge at infinity?
I stand up and I look at two parallel railroad tracks. I find that converge away from me. Why? Can someone explain me why parallel lines seem to converge, please?
Why do people have darker skin in sunnier climates? What is the best way to clean the sensor on a interchangeable lens camera (mirrorless or digital SLR)? can I change value of $_SERVER['DOCUMENT_ROOT']? How to change Windows 7 date format? Is it possible to configure Windows 7 to use YYYY-MM-DD instead of DD/MM/YYYY as the date format? How? Where? Combining multiple git repositories Installing Guest Additions causing problems I am trying to install Guest Additions in VirtualBox with Windows XP host and Ubuntu 12.04 guest. I followed the above steps:  Devices-&gt; Insert Guest Additions CD Image. After that I locate the folder /media/VBoxAdditions4.3.4_91027/ and run sudo ./VBoxLinuxAdditions.run   I want to be able to create shared folders and adjust the resolution of the screen. I achieved to do the first issue, but I couldn't do the second one. I didn't get any message, however it is not possible to change the resolution of the screen and I cannot switch to fullscreen. What am I doing wrong?  I found in the instal log the following message: unknown version of the X Window System. I've tried the solution of the proposed link but I got the following message:  Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies: virtualbox-guest-x11 : Depends: xorg-video-abi-11                     Depends: xserver-xorg-core (&gt;= 2:1.10.99.901) E: Unable to correct problems, you have held broken packages.   I tried also to install with the command sudo apt-get install virtualbox-guest-dkms but nothing is changing. During the installation of dkms I got the message: Error! Bad return status for module build on kernel 3.13.0-32-generic(i686). Combine 4 cells in a table Here is a simple table.  I want to merge 4 cells. I want to combine the three "this" cells area in this table. I thought I have to use multirow and multicolum at same time. However, I could not find how to use it.  If possible, could you post the modified LaTeX source code?     My LaTeX code:  \documentclass{article} \usepackage{multirow}% http://ctan.org/pkg/multirow \usepackage{hhline}% http://ctan.org/pkg/hhline \begin{document}  \begin{table}[ph] \begin{center} \begin{tabular}{c|c|c|c|c} \hline \multirow{2}{*}{Raaa (k)} &amp; \multicolumn{4}{c}{C ()} \\ \hhline{~----}  &amp; 3.3 &amp; 2.5 &amp; 1 &amp; 0.5 \\ \hline \multirow{2}{*}{Raaa (k)} &amp; \multirow{2}{*}{this} &amp; this &amp; 0.5 &amp; 0.6\\ \hhline{~~~--}            &amp;                       &amp; this &amp; 0.7 &amp; 1.2 \\ \hline \end{tabular} \caption{R, C ripple size} \label{T:peak} \end{center} \end{table} \end{document} Fontspec causes long underscores My collaborator added \usepackage[no-math]{fontspec} to a document we're working on. The result is that \_ underscores become v. long: cf. pictures below.   \documentclass{article} \usepackage[no-math]{fontspec} \pagestyle{empty}  \begin{document} \textrm{metric\_space} \end{document}   With fontspec:    Without fontspec:   The underscores are about twice as long with fontspec, and also much thinner. My question is, how do I get back to the original width? (Ideally I would like to preserve the thinness -- it looks much nicer than the original.)  In case someone asks, "why are you using \_?", the short answer is that I need to typeset identifiers involving an underscore. See  for an example in context. I'd be happy with using something other than \textrm, if it looks decent in the context of that example. Algebraic Proof that $\sum\limits_{i=0}^n \binom{n}{i}=2^n$ Just watched the 'How Big is the Universe?' TV program and it indicated that the universe is believed to be infinite in size. They used an approach involving measuring the internal angles of triangles. Or something like that anyway.  But hang on, the Universe has a known starting time and size followed by a finite time expanding at a finite speed. So surely, by definition, it cannot be infinite? I can accept it is honking big but by definition it cannot be infinite. Are they misleading me? Can I see why a package is installed? Short science fiction film about a Midwest farmer who builds a bunker after finding a space plant How to input integer value to an array, based preceeding row + column values? Is a continuous function on a bounded set bounded itself? If $f\colon A\to\mathbb R$ is continuous and $A$ is a bounded set, does it necessarily follow that $f$ is bounded? What is the best way to iterate over a dictionary? I've seen a few different ways to iterate over a dictionary in C#.  Is there a standard way? How do I craft command blocks? I went to my friends house, and he was playing Minecraft on the PC. He showed me a command block, but when I went home and opened Minecraft pocket edition, I went to the crafting table but I could not find any command blocks to craft.  What are command blocks and how do I craft them? I have a character playing a multiclass Barbarian/Monk. Does the resistance from rage combine with Deflect Missiles to negate the damage and make the reaction attack? How do you display a photo map tip in QGIS 3 on Windows?  As a new user I'm not sure if this is my lack of experience or a bug, so I've tried to simplify it as far as I can:  This is the contents of the Layer Display properties.    &lt;div style="width:400;height:400"&gt; &lt;p&gt;test&lt;/p&gt; &lt;div&gt;&lt;img src="C:\Local\aa.jpg" width="350" /&gt;&lt;/div&gt; &lt;/div&gt;   and this is how it appears:    C:\Local\aa.jpg is real file I'm using to try to figure out what the problem is. What am I doing wrong? Where can I safely store my stuff? I'd like to find a place to store stuff while I'm out adventuring, without spending 5000 on a house (at least, until I can afford that...). Where can I safely store items without worrying about them disappearing?   There are two possible places that come to mind,  (to which I have the key and was told I could stay), and the small bedroom given to me at the  (which I was told was mine, despite seeing J'zaro sitting in it later). Can I store items safely in either of these places? A continuation of .  I'm fighting a page-limit in a single-column layout and I need to put a Figure and a Table side-by-side and provide them with independent captions. However, the style guide for the publishers (LNCS) wants Figure captions below and Table captions above (probably something to do with ).   =======================================================  If I adapt @lockstep's floatrow example from  accordingly to have a Table caption above ...  \documentclass{article}  \usepackage{floatrow} % Table float box with bottom caption, box width adjusted to content  %% ********************************** %% just adding \captop to original example %% ********************************** \newfloatcommand{capbtabbox}{table}[\captop][\FBwidth]  \usepackage{blindtext}   \begin{document}  \blindtext  \begin{figure} \begin{floatrow} \ffigbox{%   \rule{3cm}{3cm}% }{%   \caption{A figure}% } \capbtabbox{%   \begin{tabular}{cc} \hline   Author &amp; Title \\ \hline   Knuth &amp; The \TeX book \\   Lamport &amp; \LaTeX \\ \hline   Knuth &amp; The \TeX book \\   Lamport &amp; \LaTeX \\ \hline   Knuth &amp; The \TeX book \\   Lamport &amp; \LaTeX \\ \hline   \end{tabular} }{%   \caption{A table}% } \end{floatrow} \end{figure}  \end{document}   =======================================================  The problem becomes clear ...    =======================================================  The floatrow doesn't correctly line up the Table and Caption. I reluctantly tried to use vspace to solve the problem, but it didn't work out.  Any suggestions on how to get these two to align? I'm happy to accept any alignment that ensures that the Table and Figure fit within the same "box".  (A similar-ish question was , but specific for subfig and with a very localised problem it seems.)