Where to or how to ask "Best of" Questions for what software tools to use
How can I encourage Stack Overflow to rein in the 'subjective' vigilantes?
I recently updated my operating system from Ubuntu 13.04 to Ubuntu 13.10. Since then, I am facing difficulties compiling my TeX code in which the french babel package is called. Please note that all my sources were compiling very fine before the system upgrade. However, now, given the following header:   \usepackage[francais]{babel}  I receive the following error:  ! Package babel Error: Unknown option `francais'. Either you misspelled it   What should I do? Please note that if I remove this part of code (\usepackage[francais]{babel}), everything is compiling well. I also tried it with french, and I receive the same result. Thank you in advance for your help.  MINIMUM WORKING EXAMPLE : \documentclass[11pt,a4paper]{article} \usepackage[utf8]{inputenc} \usepackage[francais]{babel} \usepackage[T1]{fontenc} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb}  \begin{document} This is a MINIMUM WORKING EXAMPLE. \end{document}   ! Package babel Error: Unknow option `francais'. Either you misspelled it Is there a way to change the environment variables of another process in Unix? Determining a matrix from its characteristic polynomial Let $A\in\mathcal{M}_{n}(K)$, where $K$ is a field. Then, we can obtain the characteristic polynomial of $A$ by simply taking $p(\lambda)=\det(A-\lambda I_n)$, which give us something like $$p(\lambda) = (-1)^n\lambda^n + (-1)^{n-1}(\text{tr } A)\lambda^{n-1} +  \cdots + \det A$$ Now, how can we obtain the matrix $A$ knowing the characteristic polynomial? Solve $x^2+2=y^3$ using infinite descent? How do I specify a pointer to an overloaded function? Prove by Double Counting Method $\sum\limits_{k = 0}^m \binom{m}{k}\binom{n}{r + k} = \binom{m + n}{m + r}$ Show by combinatorial arguments that:   $$\sum_{k = 0}^m \binom{m}{k}\binom{n}{r + k} = \binom{m + n}{m + r}$$  Hello ,  I want to prove this argument by double counting method, i kinda have an idea of proving by comb args. but not by double counting... Can someone give any clues or ideas? thanks :) Can sum of a rational number and its reciprocal be an integer?   My brother asked me this question and I was unable to answer it.   The only trivial solutions which I could think of are $1$ and $-1$.  As to what I tried, I am afraid not much. I have never tried to solve such a question, and if someone could point me in the right direction, maybe I could complete it on my own.  Please don't misunderstand my question.   I am looking for a rational number $r$ where $r + \frac{1}{r}$ is an integer. I try to share my internet connection from my laptop (win7) via virtual wifi to my android phone (Samsung Gio). In an elevated cmd I enter  netsh wlan set hostednetwork mode=allow ssid=VWiFi key=xxx keyUsage=persistent netsh wlan start hostednetwork   The android phone connects to VWifi, but the internet connection is hardly usable on the phone while the internet connection on my laptop is very good at the same time (some Mbps)  What works: I can start WhatsApp, type and receive text messages, so I guess there's no general problem, i.e. config can't be completely wrong - but when I try to send pics or audio or try to receive pics or audio messages then I see from the network monitor on my laptop that the connection doesn't even try to send or receive anything (0 kbps up/down).  What sometimes works: connection to some websites with acceptable speed - but sometimes I don't get a single byte. Also this is not reproducible - the same website sometimes shows up, sometimes android tells my the site was not available.  What never worked so far: connecting to Google Play Store. It always tells me to check my connection and try again.  What I tried so far: I read on problems with IPv6, but no matter if I enable or disable IPv6 in the settings of the virtual Wifi, it doesn't help.  I also read about problems related to static/dynamic IPs, my netsh interface ip show config tells my that dchp isn't enabled on my virtual Wifi connection. If I try to enable it by netsh interface ip set address "myWificonnection" dhcp the android phone won't even connect anymore to the virtual Wifi at all. So there may be a solution here if android would connect with dhcp enabled.  I also read about problems with MAC filters, but this is no router, there's no MAC filter in the virtual Wifi.  When I directly connect to a real WLAN router, everything is fine and working. I have the problems only when trying to get into the internet via the virtual Wifi.  Any ideas what may be configured wrong? Either on laptop or on android? Thanks. Installing particular versions when repo has newer versions? Box around single element in list Is there any way in latex to create a simple box around one item in a list?  I tried both \framebox, and \fbox, none of them worked  \begin{enumerate}[label=\Alph*),ref=\Alph*] {\color{red}\item null.}  \item lik vektdifferansen $GT - GK$. \item lik vektsummen $GT + GK$. \item lik vekten av $K$. \end{enumerate}   Works, but   \begin{enumerate}[label=\Alph*),ref=\Alph*]  {\color{red}  \fbox{ \item null.} }   \item lik vektdifferansen $GT - GK$. \item lik vektsummen $GT + GK$. \item lik vekten av $K$. \end{enumerate}   Does not. So yeah, any way to box a single entry in a list? Sci-fi novel involving living forever through teleporter copies How to pass the values from one activity to previous activity Kill some processes by .exe file name On which Canary island is it possible to sleep on the beach? We are planning a two-night trip to the Canary Islands. The cheapest options include Lanzarote and Las Palmas for flights. Travel dates are last week of November, so I guess weather should be okay. I have never been to these islands. I'd like to sleep on the beach in a tent or mattresses. Is that possible, safety, legality, and weather? It would also be nice to know how populated with tourists the islands are. why would curl and wget result in a 403 forbidden? Proving of Integral $\int_{0}^{\infty}\frac{e^{-bx}-e^{-ax}}{x}dx = \ln\left(\frac{a}{b}\right)$ Prove that      $$ \int_{0}^{\infty}\frac{e^{-bx}-e^{-ax}}{x}\,dx = \ln\left(\frac{a}{b}\right) $$   My Attempt:  Define the function $I(a,b)$ as  $$ I(a,b) = \int_{0}^{\infty}\frac{e^{-bx}-e^{-ax}}{x}\,dx $$  Differentiate both side with respect to $a$ to get  $$ \begin{align} \frac{dI(a,b)}{da} &amp;= \int_{0}^{\infty}\frac{0-e^{-ax}(-x)}{x}\,dx\\ &amp;= \int_{0}^{\infty}e^{-ax}\,dx\\ &amp;= -\frac{1}{a}(0-1)\\ &amp;= \frac{1}{a} \end{align} $$  How can I complete the proof from here? How do I make a Villager Trade a Spawn Egg selectively make contact groups silent the teacher gave me this problem to solve. So i hope you can help me with it. Here is the problem: John poured 150ml ob boiling water in 2 cups made out of polystyrene. Cups are open on the top so heat goes out there. Temperature of the outside air is 20°C. In 1 cup he add 5 mm thick layer of hot oil. He measured starting temperatures and then he measured temperatures again after 10 min. He measured the mass of water and water+oil before and after 10 min.  Here are the resaults:   -cup 1 (only water)  starting temp: 96°C  finnish temp: 64°C  starting mass: 149.4g  finnish mass: 142.42g  -cup 2(with oil on top)  starting temp.: 96°C  finnish temp.:91°C  starting mass: 164.72g  finnish mass: 164.70g  The surface of the both cups is 0.003 m2  Questions: 1.Why did the water covered with oil cooled down slower that the one with no oil? Show with calculations. 2.Why did John use oil with temperature around 100°C and not oil with room temperature? How would the resaults change if he used room temeprature oil? 3. Which other physical values, which are relevant, can you calculate from this informations? Basiccaly i need the physics behing why does this happen. Matrix doesn't shrink when put in fraction.