How to proof the inequality related to Schwarz lemma?
Inequality similar to the Schwarz-Pick theorem
Flight ticket reimbursement after Travel Warning I've got a round-trip flight with Royal Air Maroc from Strasbourg, France (SXB) to Ouagadougou, Burkina Faso (OUA) on Monday, Nov 10. Return is on Dec 1. The recent turmoils in Ouagadougou have led the US Department of State for Travels to issue a , which is why I'd like to refrain from the trip.  Any chance I can get a reimbursement for my tickets? In Germany (where I live), an official travel warning can help you get a refund when you book a trip with a tour operator/travel agency, but in this case I booked the flight directly with a non-German airline, so German law surely doesn't apply here.  EDIT: Sorry for failing to state this earlier, but I had already called the airline as suggested in the answers. They had told me it's not possible to get a refund with my standard fare. However, I understand that sometimes you really have to bargain to get a refund, so I wanted to learn about similar experiences and possibly about some hard (legal) facts that I could bring forward. Do electrical devices "take what they need" One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them.   If a motor needs 12 volts and 500ma and I supply it with 12 volts and 3000ma will it only consume 500ma? Also, if I supply it with 15volts and 500ma what will happen?   It seems logical that an LED and a DC motor are way different when it comes to requiring/using electric where as an led has to be completely regulated and (I assume) a DC motor doesn't.   Is my understanding wrong? How to move and overwrite subdirectories (and files) to parent directory? If an email message contains an email address in the body, Gmail automatically converts it into a mailto: link, which is helpful.  And many times each day I've enjoyed being able to right-click a mailto: link in an email (within Gmail) and then click "Copy email address" in the context menu.  Then I can paste that email address into a program (such as when I want to search a database).  However, within the past month or so, I've noticed that I can't right-click and click "Copy email address" without Gmail then popping open a "New Message" panel and changing my current URL to have ?compose=new at the end.  I wonder if it's related to .  How can I disable it?  I'm tried of having to click the "Discard draft" trash can button so many times throughout the day. How can I echo a newline in a batch file? How can you you insert a newline from your batch file output?  I want to do something like:  echo hello\nworld   Which would output:  hello world Some of the git commands have many options, and it would often be useful to search through them for the one I need - I was just looking for the option which controls the TAB width in git-gui, but there are about 200 completions for git config. An obvious workaround is to copy all the completions into an editor and search through them, but I'd rather do  [something] | grep tab   There are no man or info pages for compgen, help compgen doesn't even explain its own options, and there's no auto-complete for compgen (how's that for irony?).  PS:  doesn't work.  PPS: This is not a question about git-gui - The  was elsewhere.  PPPS: This is not about auto-completing commands, only command parameters. I'm using LyX on Linux Mint 14 ...  Using BibTeX with the apalike style and some modifications in the preamble, I've managed to get the bibliography as it should be except for one thing. When I cite a work with multiple authors it gets printed with the separator "and" which isn't correct for my language (Danish). Curiously it's displayed correctly in the user interface of Lyx - for example "(Wittgenstein og Waismann 2003 - which led me to believe everything was ok but in the pdf the separator "and" is used both in the reference and in the bibliography.  Is there any way to fix this using BibTeX, or can it only be done with biber 1.5, as suggested in the last comment here:   I really hope their is because getting biber to work using the following guide has thus far proven to be impossible:   Help much appreciated ... I really hope I won't have to relapse into setting my master thesis up in LibreOffice. Giving edit reputation bonus for same user for same post multiple times On Stack Overflow, I saw some users editing the same question multiple times, and getting the 2 point reputation bonus for each time.  I saw it during review of a suggested edit (some months ago, I forgot the question that's why I'm unable to paste the link here). I rejected it and gave the reason in the "Other" reason field.  Most of the time I saw that users first formats the code, and then after approval they edit the title and fix the grammar.  Why is this allowed?  My point is, if an user gained 2 reputation points for a particular edit, then why give another 2 points again for the same post? Because the second edit on same question/answer means that there were some mistakes or misses in their previous edit. I tried to export my Geogebra graphs into tikz-code. In General it works fine, but plot x^1/3 doesn't work:  \documentclass[10pt]{article} \usepackage{pgf,tikz} \usetikzlibrary{arrows} \pagestyle{empty} \begin{document} \definecolor{ccqqqq}{rgb}{0.8,0,0} \definecolor{qqttcc}{rgb}{0,0.2,0.8} \definecolor{cqcqcq}{rgb}{0.75,0.75,0.75} \begin{tikzpicture}[line cap=round,line join=round,&gt;=triangle 45,x=1.0cm,y=1.0cm] \draw [color=cqcqcq,dash pattern=on 1pt off 1pt, xstep=1.0cm,ystep=1.0cm] (-4,-4) grid (4,4); \draw[-&gt;,color=black] (-4,0) -- (4,0); \foreach \x in {-4,-3,-2,-1,1,2,3} \draw[shift={(\x,0)},color=black] (0pt,2pt) -- (0pt,-2pt) node[below] {\footnotesize $\x$}; \draw[-&gt;,color=black] (0,-4) -- (0,4); \foreach \y in {-4,-3,-2,-1,1,2,3} \draw[shift={(0,\y)},color=black] (2pt,0pt) -- (-2pt,0pt) node[left] {\footnotesize $\y$}; \draw[color=black] (0pt,-10pt) node[right] {\footnotesize $0$}; \clip(-4,-4) rectangle (4,4); \draw[color=qqttcc, smooth,samples=100,domain=-4.0:4.0] plot(\x,{(\x)*(\x)*(\x)}); \draw[color=ccqqqq, smooth,samples=100,domain=-4.0:4.0] plot(\x,{((\x))^(1/(3))}); \draw [color=qqttcc](2.06,4.18) node[anchor=north west] {$f(x)=x^3$}; \draw [color=ccqqqq](2.06,1.18) node[anchor=north west] {$f(x)=\sqrt[3]{x}$}; \begin{scriptsize} \draw[color=qqttcc] (-1.74,-7.16) node {$f$}; \end{scriptsize} \end{tikzpicture} \end{document}      Error line 21: !Missing number, treated as zero.   So plot has problems with the negative x I suppose, but I don't know. Any help would be great! I googled it for nearly 1 hour - but no real answers.  As suggestet it rotated and mirrored the graph - works great!:  \documentclass[10pt]{article} \usepackage[utf8]{inputenc} \usepackage{pgf,tikz} \usetikzlibrary{arrows} \pagestyle{empty} \begin{document} \definecolor{ccqqqq}{rgb}{0.8,0,0} \definecolor{qqttcc}{rgb}{0,0.2,0.8} \definecolor{cqcqcq}{rgb}{0.75,0.75,0.75} \begin{tikzpicture}[line cap=round,line join=round,&gt;=triangle 45,x=1.0cm,y=1.0cm] \draw [color=cqcqcq,dash pattern=on 1pt off 1pt, xstep=1.0cm,ystep=1.0cm] (-4,-4) grid (4,4); \draw[-&gt;,color=black] (-4,0) -- (4,0); \foreach \x in {-4,-3,-2,-1,1,2,3} \draw[shift={(\x,0)},color=black] (0pt,2pt) -- (0pt,-2pt) node[below] {\footnotesize \x}; \draw[-&gt;,color=black] (0,-4) -- (0,4); \foreach \y in {-4,-3,-2,-1,1,2,3} \draw[shift={(0,\y)},color=black] (2pt,0pt) -- (-2pt,0pt) node[left] {\footnotesize \y}; \draw[color=black] (0pt,-10pt) node[right] {\footnotesize 0}; \clip(-4,-4) rectangle (4,4); \draw[color=qqttcc, smooth,samples=100,domain=-4.0:4.0] plot(\x,{(\x)*(\x)*(\x)}); \begin{scope}[yscale=-1,xscale=1] \draw[rotate=90, color=ccqqqq, smooth,samples=100,domain=-4.0:4.0] plot(\x,{(\x)*(\x)*(\x)}); \end{scope} \draw [color=qqttcc](2.06,4.00) node[anchor=north west] {$f(x)=x^3$}; \draw [color=ccqqqq](2.06,1.00) node[anchor=north west] {$f(x)=\sqrt[3]{x}$}; \begin{scriptsize} \draw[color=qqttcc] (-1.74,-7.16) node {f}; \end{scriptsize} \end{tikzpicture} \end{document} "Since", "until", "from", "to" on invoices or date ranges of a form Which is the correct form on an invoice, or a general date range in a form, and why?  Monkey dolls                        12 GBP From 2012-01-03 to 2013-01-02  Monkey dolls                        12 GBP Since 2012-01-03 until 2013-01-02   Form format (dates can be modified with a datepicker):  Since: 2012-01-03 until: 2013-01-02   Since+until makes sense and sounds ok to me, yet I know I can be very wrong, at least when it comes to the common usage in the UK and/or US, since English is not my first language.  I am interested in both British and American English.  Until now I've been using since+until, yet some articles explicitly say they may not ever be used together, while some people and some other articles get deep into grammar rules which I can't really apply on the context of invoices and forms.  Here's a recent article saying since and until can never be used together (last paragraph):   Edit: The date range can start in the past or in the future, and can end in the past or in the future. However, at the time of issuing an invoice or rendering a form, you cannot know when the document will be read or how the form will be filled. We had in our lecture on numerical analysis the following: Let $\mathrm{Lin}(X,Y)$ be the set of all linear maps $X\rightarrow Y$. Let $A\in\mathrm{Lin}(\mathbb R^l,\mathbb R^n)$ and $B\in\mathrm{Lin}(\mathbb R^n,\mathbb R^m)$ and $\|C\|_{op}:=\max_{\|x\|\leq1}\|C(x)\|$. Then our lecturer followed $\|A\circ B\|_{op}\leq\|A\|_{op}\cdot\|B\|_{op}$. So he didn't prove it and so I've tried it by my own. My attempt: $$\begin{aligned} \|A\circ B\|_{\mathrm{op}} &amp;= \max_{\|x\| &lt; 1}\|(A \circ B)(x)\| \\ &amp; \leq \max_{\|x\| &lt; 1} \|A\|_{\mathrm{op}} \|B(x)\| \\ &amp;= \|A\|_{\mathrm{op}} \max_{\|x\|\leq1}\|B(x)\|\\ &amp;= \|A\|_{\mathrm{op}}\|B\|_{\mathrm{op}} \end{aligned}$$ But this seems too easy. I am really interested in a nice proof so anybody could help? Thanks a lot! What are Click packages? I noticed that Ubuntu SDK recently had some updates and it installed a program named "Click". I would like to know what they are and how to use them.  Also, would they make Debian packaging easier? I have two tables in my database:  NEWS table with columns:   id - the news id  user - the user id of the author)   USERS table with columns:   id - the user id   I want to execute this SQL:   SELECT * FROM news JOIN users ON news.user = user.id    When I get the results in PHP I would like to get associative array and get column names by $row['column-name']. How do I get the news ID and the user ID, having the same column name? What is a "Nested Quantifier" and why is it causing my regex to fail? I have this regex I built and tested in regex buddy.  "_ [ 0-9]{10}+ {1}+[ 0-9]{10}+ {2}+[ 0-9]{6}+ {2}[ 0-9]{2}"   When I use this in .Net C#   I receive the exception  "parsing \"_ [ 0-9]{10}+ +[ 0-9]{10}+  +[ 0-9]{6}+  [ 0-9]{2}\" - Nested quantifier +."   What does this error mean? Apparently .net doesn't like the expression.  Here is the regex buddy so u can understand my intention with the regex...  _ [ 0-9]{10}+ {1}+[ 0-9]{10}+ {2}+[ 0-9]{6}+ {2}[ 0-9]{2}  Match the characters "_ " literally «_ » Match a single character present in the list below «[ 0-9]{10}+»    Exactly 10 times «{10}+»    The character " " « »    A character in the range between "0" and "9" «0-9» Match the character " " literally « {1}+»    Exactly 1 times «{1}+» Match a single character present in the list below «[ 0-9]{10}+»    Exactly 10 times «{10}+»    The character " " « »    A character in the range between "0" and "9" «0-9» Match the character " " literally « {2}+»    Exactly 2 times «{2}+» Match a single character present in the list below «[ 0-9]{6}+»    Exactly 6 times «{6}+»    The character " " « »    A character in the range between "0" and "9" «0-9» Match the character " " literally « {2}»    Exactly 2 times «{2}» Match a single character present in the list below «[ 0-9]{2}»    Exactly 2 times «{2}»    The character " " « »    A character in the range between "0" and "9" «0-9»   In short...  What is a Nested quantifier? Are the rings $k[[t^3,t^4,t^5]]$ and $k[[t^4,t^5,t^6]]$ Gorenstein? (Matsumura, Exercise 18.8) Here is question 18.8 of Matsumura's Commutative Ring Theory. It asks whether the rings   $k[[t^3,t^4,t^5]]$, $k[[t^4,t^5,t^6]]$   are Gorenstein. I got that 1) is not Gorenstein, but 2) is Gorenstein (by computing the socle). Just wanted to check if I am correct. I don't need the answer necessarily, a yes or a no will suffice. Thanks. How to get more info out of the uninformative Windows 8 BSOD? Has 'Ubuntu Software' been renamed to 'Snap Store'? I updated Ubuntu last night (sudo apt get update &amp;&amp; sudo apt get upgrade) and to  my surprise this morning I didn't find the 'Ubuntu Software' app and there's a new entry called 'Snap Store' which when opened looks just like the old 'Ubuntu Software' app. So has 'Ubunu Software' been renamed to 'Snap Store'? And if yes, why? I'm pretty new to this and this is my first question here, any help would be greatly appreciated.  So basically what I want to achieve is a floor material as seen in this photo...    ...the reflections are very crisp but dim.  With a glossy shader I get the following results:    First picture: reflections are blurry  Second picture: roughness of the material looks right but reflection is bright red  Third picture: If tinted in any other color than white, it seems to produce the result I want. Reflection is sharp and gets tinted blue. What I need is the reflection to be tinted white.  Thanks for any help. Virtualbox Windows 10 Guest installation is freezing up in 14.04 I've installed VirtualBox using the Software Centre and I'm running a system on Ubuntu 14.04 with 8gb RAM, 64-bit dual core processor.  I want to run Windows 10, I've tried both 64 and 32 bit versions, in virtualbox. However, every time I start up windows 10 it gets to the point where the dots go round in a circle, then it freezes up and crashes back to the virtualbox manager. The only information it gives me is that the virtual machine was aborted.  I've changed the settings around a lot and nothing is working.  Any help would be appreciated.  Oh, and I've run Windows 10 technical preview on this machine before, a while ago  Thanks for any help in advance. SQL server Read Only permission automatically for new databases