Comma needed in 30-day, money-back guarantee?
Should there be a comma in 'a 30-day, money-back guarantee'?
Metric on Cartesian Product I'm currently stuck on an exercise where I need to show that if $(M,d)$ and $(N,\rho)$ are metric spaces, then $d_2((a,x),(b,y)) := \sqrt{d(a,b)^2 + \rho(x,y)^2}$ defines a metric on $M\times N$. I've already shown that the basic criteria of a metric are met, but I still need to show that the triangle ineqaulity holds.  I've tried using the triangle inequality on $d$ and $\rho$ and estimating the square root with $\sqrt{a^2+b^2}\leq a+b$, but regardless of which order I've used them in, I seem to overestimate my target. I thought maybe I somehow need to use Cauchy-Schwarz, but I don't know how. What are the best practices for modeling inheritance in databases?  What are the trade-offs (e.g. queriability)?  (I'm most interested in SQL Server and .NET, but I also want to understand how other platforms address this issue.) Reducing Lion OS Footprint by removing unnecessary files/folders I am trying to downsize my iMac 640Gb disk to make it fit onto a 120Gb (113Gb usable) SSD.  The total size of use files is currently approximately 340Gb, of which my home folder accounts for 265Gb (which I intend to not put on the SSD, or at least not all of it).  Very rough calculations suggest that my OS and application files are taking up roughly 75Gb, which puts me approximately 2/3rds full - not bad.  But, I would like to reduce this a little further if possible, to ensure that as and when I continue to use the computer (and I have a number of large apps that do not currently have installed including music production apps with a lot of data) I am not worried about running out of space on the boot drive.  To this end I already own XSlimmer which I will use periodically to remove PowerPC and language variants from my apps, but I was wondering if there are any areas of the Base OS that I can safely remove to save further space?  I am thinking about things like OS localisation, the location of the included screensavers and wallpapers, the voice files that are used for text-to-speech etc.  Is there a significant amount of such data that can be easily removed to save a few extra Gb on the boot disk? I heard about nautilus-gksu and would like to install it. Unfortunately, when I try, I get this:  glemi@XPS:~$ sudo apt-get install nautilus-gksu Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package nautilus-gksu   How and where can I get this package? I have a battery pack of NiMH batteries. It is ten cells with 1.2V, 4000mAh each, put together in series. So rated voltage is 12V. After charging, i.e. when the charging device says that it is finished, I measure 14.3V.   When I now discharge, at what voltage should I consider my battery as "empty"? Is this the lowest voltage that I can discharge it to without damaging it? Which voltage is that? I'm trying to write an automated test of an application that basically translates a custom message format into an XML message and sends it out the other end.  I've got a good set of input/output message pairs so all I need to do is send the input messages in and listen for the XML message to come out the other end.  When it comes time to compare the actual output to the expected output I'm running into some problems.  My first thought was just to do string comparisons on the expected and actual messages.  This doens't work very well because the example data we have isn't always formatted consistently and there are often times different aliases used for the XML namespace (and sometimes namespaces aren't used at all.)  I know I can parse both strings and then walk through each element and compare them myself and this wouldn't be too difficult to do, but I get the feeling there's a better way or a library I could leverage.   So, boiled down, the question is:  Given two Java Strings which both contain valid XML how would you go about determining if they are semantically equivalent?  Bonus points if you have a way to determine what the differences are. Accessing Email logs using REST or SOQL Where can I find a complete reference for the $PS1 variable? The default PS1 variable on my machine (Kubuntu 13.10) is this:  \[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\u@\h:\w\$   I'm looking for a reference for how the $PS1 variable works that, at a minimum, allows me to understand the above PS1 variable. When will L1 regularization work better than L2 and vice versa? Basic mathematical induction regarding inequalities Prove that the derivative of an even differentiable function is odd, and the derivative of an odd is even. Cumulative Sum without Script Accidently deleted boot option on Dell laptop I have a Dell laptop in which I have dual booted Ubuntu with Windows 10. Usually the laptop loads the Grub menu first.  Recently I had some problems with Windows Bitlocker: every time I open Windows I am prompted to enter the Bitlocker password. In trying to solve this, I accidentaly clicked Ubuntu in the "Delete Boot" option in the boot sequence. Now the laptop boots directly to Windows without first loading the Grub menu.  Luckily, when I restarted the system and clicked "add boot option" I found the efi folder in which the Ubuntu folder is present. In Ubuntu there is fwgrupx64.efi, grubx64.efi, grub.cfg, shimx64.efi, mmx64.efi, and BOOTX64.CSV. On clicking grubx64.efi it shows "Boot name not found".  How can I recover the Grub boot menu? What is polarisation, spin, helicity, chirality and parity? Polarisation, spin, helicity, chirality and parity keep confusing me. They seem to be related, but exactly how they are related is unclear to me. Can someone maybe give a short overview about what these quantities mean and how they are related? What are the values for e.g. basic particles like electron or photon? How to change font-size, number of rows / columns in the console I'm running a Linux server without X11 or any kind of GUI, with a modern 22" LCD monitor.  Given the huge size of my monitor, I would like to increase the number of rows and columns in my console, how can I go about achieving it? Can't we compute $\lim_{n \to \infty}\frac{1+ \cdots +n}{n^2}=\lim_{n\to\infty}\frac{1}{n^2}+\cdots +\lim_{n\to\infty}\frac{n}{n^2}=0$? Clean URLs and php extension on nginx I've looked at dozens of other questions and references on the web - and by all my calculations, my setup should work, but it doesn't.  I have nginx installation with php-fpm.  If I try to access a .php file, it runs correctly and I get the correct results.  I got this in my config file:  location ~ \.php$ {     try_files $uri =404;     fastcgi_pass unix:/var/run/php5-fpm.sock;     include fastcgi_params;     fastcgi_param SCRIPT_FILENAME  $document_root$fastcgi_script_name; }   Now, I want to setup my web app so that /somedir/file automatically executes /somdir/file.php while still displaying /somdir/file in the browser's address bar.  So I modified my config to contain the following:  location / {     try_files $uri $uri/ $uri.php?query_string }   This kind of works, that is, the server does access the .php file.  Yet, instead of executing it using the existing location ~ \.php$ block above, it simply spits the php source code as the download into the browser.  If I append the .php manually to the requested URL, then the php is executed.  It feels as if once the server matches try_files to $uri.php, it then does not do another pass at locations to see that what it needs to do with the php files.  I tried putting the php block above and below the location /, but it makes no difference.  How can I get the php to be executed? Let $A,B$ be any two sets. I really think that the statement $|A|\leq|B|$ or $|B|\leq|A|$ is true. Formally:     $$\forall A\forall B[\,|A|\leq|B| \lor\ |B|\leq|A|\,]$$   If this statement is true, what is the proof ? Does a wing in a potential flow have lift? How to solve and see resolution of $13^{53} \pmod 7$ using Fermat little Theorem?