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How is "Can anyone tell me how can I solve this" wrong? Can we create a subsection of the References Cited section with different reference numbering? Can a continuous real function take each value exactly 3 times? Clicking on tags in global search results is broken Calculating size of particular area below buffer in QGIS? I have a point shapefile of villages where data was collected in Northern Kenya. I created a buffer around those villages.   The second vector layer contains polygons defining areas according to vegetation type. So for example, a forest might be surrounded by a narrow ring of woodland in an area which is mainly grassland. I'm trying to obtain a percentage of each vegetation type within the buffer per village.   I'm using QGIS 1.7 Android cancel Toast when exiting the app and when toast is being shown How do I make protocol foo hostname-aware? This is a  about hostname-awareness and proxying.   I know that some protocols are hostname-aware; that is, when I connect to the HTTP server at www.example.com it knows I want www.example.com's HTTP service, not www.example.net's, even though they are on the same IP address.  How can I do this for protocol foo?  (Temporary note: this question appears pursuant to .) I got multiple entry schengen visa issued by Greece. Can I directly travel from India - Qatar - Romania or through schengen state How to loop over the lines of a file? How can I detect inside a TeX file which engine (pdftex/xetex/luatex) is used to compile the file? Is there a LaTeX package that provides this functionality? If I have random variables $X_1,X_2,\ldots,X_n$ that are Poisson distributed with parameters $\lambda_1, \lambda_2,\ldots, \lambda_n$, what is the distribution of $Y=\left\lfloor\frac{\sum_{i=1}^n X_i}{n}\right\rfloor$ (i.e. the integer floor of the average)?  A sum of Poissons is also Poisson, but I am not confident enough in statistics to determine if it is the same for the case above. How to start X windows inside "Bash on Ubuntu on Windows" After installing the new feature (still "Beta") called  that is a feature subset of Windows 10 Anniversary edition, I get the following message when trying to start X-Windows using startx :    What do I need to tweak / configure in order for X-Windows to launch?  I noticed that xauth was already installed, however I had to install the rest of the framework as follows :  apt-get install xorg openbox Delay in approval leads to missing out on being awarded an "Explainer" badge It is perhaps a bit embarrassing that while doing higher-level math, I have forgot some more fundamental concepts. I would like to ask whether the square root of a number includes both the positive and the negative square roots.  I know that for an equation $x^2 = 9$, the solution is $x = \pm 3$. But if simply given $\sqrt{9}$, does one assume that to mean only the positive root? And when simply talking about the square root of a number in general, would one be referring to both roots or just the positive one, when neither is specified? Updated WiFi fix for Yoga 13 and Ubuntu 16.04? How to read a file line-by-line into a list? proving roots of equation $x^2+x+4f=0$ are real. Let $a,b,c$ be three positive real numbers such that $a+b+c=1$. Let $f=\min(a^3+a^2bc, b^3+ab^2c,c^3+abc^2)$. Prove that the roots of the equation $x^2+x+4f=0$ are real. In my book, the following are described to be the steps that one must follow if he wishes to find the direction of static friction force acting on an object:  &quot;(1) Draw the F.B.D(free body diagram) of the object in question with respect to the other object on which it is kept. (2) Include the pseudo force also, if the contact surface is accelerating. (3) Decide the direction of the resultant force and resolve this force into two components; one along the surface of contact and the other along the normal to this surface. (4) The direction of static friction is opposite to the component of the result force along the contact surface.&quot;  Firstly, are these steps correct? Will I always obtain the correct answer by following these steps? Secondly, consider the following problem:  In questions like these, when I try to find the resultant force and then assign the direction to static friction, I find that my answer is incorrect! Are there some other steps to follow when I know that the object is definitely accelerating in one direction or another? Edit 1: I approached the above question by doing exactly what my book suggests; first, I identified all the forces acting on the smaller block, being the normal force applied by the block A and its weight mg downward. Adding these two forces, I get another force that actually acts on the body like so:  I wonder if I'm not supposed to take either of the contact forces into consideration when drawing the F.B.D to figure out the direction of static friction acting on the body. Also, are there other steps for finding the direction of kinetic friction? Edit 2: From Judge's answer, I have been able to figure out my mistake, it being that I completely missed step (3) and didn't resolve the resultant force into components! Sheesh. Sorry! Much thanks in advance! :) Regards. I admin a handful of cloud-based (VPS) servers for the company I work for.   The servers are minimal ubuntu installs that run bits of LAMP stacks / inbound data collection (rsync). The data is large but not personal, financial or anything like that (ie not that interesting)  Clearly on here people are forever asking about configuring  and such like.   I use a bunch of approaches to secure the servers, for example (but not restricted to)   ssh on non standard ports; no password typing, only known ssh keys from known ips for login etc https, and restricted shells (rssh) generally only from known keys/ips servers are minimal, up to date and patched regularly use things like rkhunter, cfengine, lynis denyhosts etc for monitoring   I have extensive experience of unix sys admin. I'm confident I know what I'm doing in my setups. I configure /etc files. I have never felt a compelling need to install stuff like firewalls: iptables etc.  Put aside for a moment the issues of physical security of the VPS.  Q? I can't decide whether I am being naive or the incremental protection a fw might offer is worth the effort of learning / installing and the additional complexity (packages, config files, possible support etc) on the servers.  To date (touch wood) I've never had any problems with security but I am not complacent about it either. How do you parse and process HTML/XML in PHP?