I am looking for a way to disable/enable a specific key (e.g. backspace) from the command line.  Any suggestions?
I have a laptop with a full keyboard (it has numpad), but the laptop is not that big, and because of that the keys are relatively small, which means I am constantly finding myself pressing keys accidentally on the numpad part.  Is there a way to disable specific keys that I simply don't want?
Is there an example of a ring $S$ with identity $1_S$ containing a non-trivial subring $R$ which itself has an identity $1_R$, but $1_R\neq 1_S$ (or equivalently $1_S\notin R$). I'd also like to know under what conditions the identities have to be equal. I know they must be equal if $S$ has no zero divisors, since for every $r\in R$ we have $(1_S-1_R)r=0$  In other words: Is the category of unital rings with identity-preserving morphisms a full subcategory of the category of rings (where morphism are only required to respect addition and multiplication)? Do I need a license to create pdf files? I hope this is the correct place where I could ask this question. My mother is an accountant with a degree in economics. She works as a freelancer and she needs some licenses for her job.  The biggest problem is adobe acrobat standard, which costs 400€, quite a lot. I want understand if she must buy it to create pdf files or she can use some free (even for commercial use) programs that she has because of her job (the chamber of commerce provide some advantages to accountants).  She is actually using PDFCreator, which as I can read is free for business usage (open source also!!):   Thanks for any suggestion Let $f$ be defined on $\mathbb{R}$ by $f(x) = e^{-1/x^2}$ for $x$ not equal to $0$. and $f(0)= 0$. Prove that $f^{(n)}(0)=0$ for all $n = 1, 2,3$ ...  Do I need to use Taylor expansion from calculus class?  Any hint would be appreciated. I'm trying to convert some LaTeX into HTML but my code listings don't preserve their code coloring. Why is that and how do I fix it?  This is what it looks like:    Side note: I'm also wondering why the caption on the table was removed.  Edit  Here is an example listing with colors:  \documentclass{article} \usepackage{color} \usepackage{listings} \lstset{     basicstyle=\footnotesize\ttfamily,     language=[Sharp]C,      keywordstyle=\color[rgb]{0,0,1.0}\bfseries,       commentstyle=\color[rgb]{0.133,0.545,0.133}\bfseries, }  \begin{document} \begin{lstlisting} int x = 10;  // This is a comment string str = "hello"; \end{lstlisting} \end{document}   This produces the following HTML when doing: htlatex myfile.tex:  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"     "http://www.w3.org/TR/html4/loose.dtd"&gt;   &lt;html &gt;  &lt;head&gt;&lt;title&gt;&lt;/title&gt;  &lt;meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"&gt;  &lt;meta name="generator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)"&gt;  &lt;meta name="originator" content="TeX4ht (http://www.cse.ohio-state.edu/~gurari/TeX4ht/)"&gt;  &lt;!-- html --&gt;  &lt;meta name="src" content="LaTeX4.tex"&gt;  &lt;meta name="date" content="2012-07-20 12:30:00"&gt;  &lt;link rel="stylesheet" type="text/css" href="LaTeX4.css"&gt;  &lt;/head&gt;&lt;body  &gt;    &lt;!--l. 12--&gt;    &lt;div class="lstlisting" id="listing-1"&gt;&lt;span class="label"&gt;&lt;a   id="x1-2r1"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;int&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;x&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;=&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;10;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;br /&gt;&lt;span class="label"&gt;&lt;a   id="x1-3r2"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;br /&gt;&lt;span class="label"&gt;&lt;a   id="x1-4r3"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;//&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;This&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;is&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;a&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;comment&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;br /&gt;&lt;span class="label"&gt;&lt;a   id="x1-5r4"&gt;&lt;/a&gt;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;string&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;str&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;=&lt;/span&gt;&lt;span  class="cmtt-8"&gt;&amp;#x00A0;&lt;/span&gt;&lt;span  class="cmtt-8"&gt;"&lt;/span&gt;&lt;span  class="cmtt-8"&gt;hello&lt;/span&gt;&lt;span  class="cmtt-8"&gt;"&lt;/span&gt;&lt;span  class="cmtt-8"&gt;;&lt;/span&gt;     &lt;/div&gt;  &lt;/body&gt;&lt;/html&gt;   Which looks like this:    I would want the HTML result to look like this: With reference to:    I removed the Cortana packages from my running Windows 10 using the method posted by magicandre1981 and using  win6x_registry_tweak.   My question is how can I re-install Cortana (or for that matter any other package removed similarly)?  I have opened up the install.wim image (converted from a Win 10 install.esd file) and found Cortana in the system apps folder, but don't know how / what to use to re-install it.  Any help please? If $a_n$ is a strictly increasing unbounded sequence, does $\sum_n \frac{a_{n+1} - a_n}{a_n}$ diverge? So I've been thinking through some test cases. If $a_n = n$ then $\sum_n \frac{a_{n+1} - a_n}{a_n}$ is the harmonic series which diverges. And if $a_n = \sum_{k=1}^n 1/k$ then $\sum_n \frac{a_{n+1} - a_n}{a_n}$ diverges like $\sum_n 1/(n \log n)$. So that got me thinking, if $a_n$ is a strictly increasing unbounded sequence, does $\sum_n \frac{a_{n+1} - a_n}{a_n}$ necessarily diverge? In some literature, I have read that a regression with multiple explanatory variables, if in different units, needed to be standardized.  (Standardizing consists in subtracting the mean and dividing by the standard deviation.)  In which other cases do I need to standardize my data?  Are there cases in which I should only center my data (i.e., without dividing by standard deviation)? In the Wikipedia article , it says     After Newtonian gravitation was found to be inconsistent with special relativity, . . .   I don't see how Newtonian gravitation itself is inconsistent with special relativity.  After all, Newton's Universal Law of Gravitation is completley analogous to Coulomb's Law, so it would seem that, if there were an analogous "gravitational magnetic field", one could formulate a theory of gravitation in exact analogy with Maxwell's Theory of Electromagnetism, and of course, this would automatically be consistent with Special Relativity.  What about this approach to gravitation does not work?  The only problem I could see with this is the lack of evidence for a "gravitational magnetic field".  That being said, gravity is "weak" as it is, and my guess is that it would be extremely difficult to set up an experiment in which a massive body were moving fast enough for this "magnetic field effect" to be obsevable.  EDIT:  As has been pointed out to me in the answers, Newton itself is inconsistent with SR.  Similarly, however, so is Coulomb's Law, yet, electromagnetism is still consistent with SR.  Thus, how do we know that it is not the case that Newton's Law is the special "static" case of a more general gravitomagnetic theory exactly analogous to Maxwell's Theory:  Let $\mathbf{G}$ be the gravitation field, let $\rho$ be the mass density, and $\mathbf{J}$ be the mass current density, let $\gamma _0$ be defined so that $\frac{1}{4\pi \gamma _0}=G$, the Universal Gravitation Constant, let $\nu _0$ be defined so that $\frac{1}{\sqrt{\gamma _0\nu _0}}=c$, and suppose there exists a field $\mathbf{M}$, the gravitomagnetic field, so that the following equations hold: $$ \vec{\nabla}\cdot \mathbf{G}=-\frac{\rho}{\gamma _0} $$ $$ \vec{\nabla}\cdot \mathbf{M}=0 $$ $$ \vec{\nabla}\times \mathbf{G}=-\frac{\partial \mathbf{M}}{\partial t} $$ $$ \vec{\nabla}\times \mathbf{M}=\nu _0\mathbf{J}+\gamma _0\nu _0\frac{\partial \mathbf{G}}{\partial t} $$ where theses fields would produce on a mass $m$ moving with velocity $\mathbf{v}$ in our inertial frame the Lorentz force $\mathbf{F}=m\left( \mathbf{G}+\mathbf{v}\times \mathbf{M}\right)$.  This theory would automatically be consistent with SR and would reduce to Newton's Law of Gravitation for the case of gravitostatics:  $\frac{\partial \mathbf{G}}{\partial t}=\frac{\partial \mathbf{M}}{\partial t}=\mathbf{J}=0$.  (To be clear, you can't just set the time derivatives equal to $\mathbf{0}$ as it seems I have done.  Upon doing so, you obtain the corresponding static theory, which is technically incorrect (as you can easily see because it won't be relativistically invariant), but is nevertheless often a useful approximation.)  My question can thus be phrased as:  without appealing directly to GR, what is wrong with this theory? Is it (always) true that $$\mathrm{Var}\left(\sum\limits_{i=1}^m{X_i}\right) = \sum\limits_{i=1}^m{\mathrm{Var}(X_i)} \&gt;?$$ Is there a tool to get the lines in one file that are not in another? Is there a reason the British omit the article when they "go to hospital"? What is the "Bootable flag" option when installing a distro? Is the "bootable flag" needed in today's distributions? If not, then why is it still in the installers? What is it exactly? USB configuration within Developer Options doesn't save How to backup all my data from a server? Is there a function in python to split a word into a list? Why do residuals in linear regression always sum to zero when an intercept is included? I'm taking a course on regression models and one of the properties provided for linear regression is that the residuals always sum to zero when an intercept is included.   Can someone provide a good explanation for why this is the case? I am looking for an application which can do the following:   Resize one or more images Compress images Rotate and flip images Rename multiple images using a progressive number or a prefix/suffix Convert an entire PDF file to a bunch images Extract an image from a Windows .ico file Convert images to DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG, TIFF, and other formats   I am running Ubuntu GNOME 15.10 with GNOME 3.18. Does $\sum \limits_{n=1}^\infty\frac{\sin n}{n}(1+\frac{1}{2}+\cdots+\frac{1}{n})$ converge (absolutely)? I've had no luck with this one. None of the convergence tests pop into mind.  I tried looking at it in this form $\sum \sin n\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}$ and apply Dirichlets test. I know that $\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n} \to 0$ but not sure if it's decreasing.  Regarding absolute convergence, I tried:  $$|\sin n\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}|\geq \sin^2 n\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}=$$  $$=\frac{1}{2}\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}-\frac{1}{2}\cos 2n\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}$$  But again I'm stuck with $\cos 2n\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}$. Assuming it converges then I've shown that $\sum \sin n\frac{1+\frac{1}{2}+\cdots+\frac{1}{n}}{n}$ doesn't converge absolutely. Since upgrading to 13.10, I can't log in to unity desktop. Light dm works correctly, but attempting to log in tries to start the session then drops back to light. I've already dropped to terminal (ctrl+alt+f2) and done this:  sudo apt-get update  sudo apt-get install --reinstall ubuntu-desktop  sudo apt-get install unity   Logging in as a guest session also fails. Logging in to other window managers works with varying degrees of success.  Note: I have Cinnamon 2.0 installed from PPA.  I'm using a 2 monitor setup.  Also of note is that the session prior to my upgrade to 13.10 the background of unity failed to display at all, instead showing what was there in the screen buffer from the previous frame. The entire OS worked correctly otherwise though, so I just ignored it for the session. No other upgrades or even updates were done prior to this occurring.  My upgrade path to 13.10 was basically this: Install 13.04 alongside Windows 7, use ubuntu as a glorified web browser for a while, get updates (in preparation for 13.10), install 13.10.  I also used Unity Tweak Tool to change some aspects of unity, particularly auto-hide.  Any help or ideas would be appreciated, as I'm typing this on my phone :( Why would turning off a sink faucet stop the shower?