Multiple apps fail to launch from Ubuntu 17.10. When I click on some of the apps  they do not launch.  i tried doing  sudo apt install unity unity --reset-icons   when i open a application for example steam), this comes up  tar: This does not look like a tar archive xz: (stdin): File format not recognized tar: Child returned status 1 tar: Error is not recoverable: exiting now find: ‘/home/jitu/.steam/ubuntu12_32/steam-runtime’: No such file or directory
I am new to Linux and I have Ubuntu 17.04 64-bit (Budgie).  I cannot open steam. It is updated to latest version. When I open it it pops up but after some time it disappears. When I try to run it from a terminal I get this output:  tar: This does not look like a tar archive xz: (stdin): File format not recognized tar: Child returned status 1 tar: Error is not recoverable: exiting now find: ‘/home/ghazi/.steam/ubuntu12_32/steam-runtime’: No such file or directory
Prove that in a triangle $$r^2+r_1^2+r_2^2+r_3^2=16R^2-(a^2+b^2+c^2)$$ where the symbols have their usual meanings. I am looking for a smaller or elegant proof using trigonometry. A geometric proof would be super cool. I did prove it but it took me ages to do the calculation. Thanks. Why is "chmod -R 777 /" destructive? This is a  about File Permission and Why 777 is "destructive".   I'm not asking how to fix this problem, as there are a ton of references of that already on Server Fault (reinstall OS). Why does it do anything destructive at all?  If you've ever ran this command you pretty much immediately destroy your operating system. I'm not clear why removing restrictions has any impact on existing processes. For example, if I don't have read access to something and after a quick mistype in the terminal suddenly I now have access well... why does that cause Linux to break? Install windows 7 through virtual box Is there an ingame way to change volume? I like the music, but I still prefer my own music.  Is there an ingame way to change the volume?   I can't find it. What can cause an answer to get deleted without information about who actually deleted it? Usually when answer gets deleted directly (i.e. not as side effect of its parent question deleted) it says "deleted by [name here] [time stamp]". Plus, it always leave a revision.  However, I just stumbled over  on Stack Overflow:        Weird, don't you think? Looking in the , nothing strange in there and nothing strange in  as well.  Finally, the last straw... :        Another thought was maybe some automagical conversion to comment, but no such comment exists.  Can anyone shed some light over this phenomenon? Getting a collection of index values using a LINQ query Is there a better way to do this?  string[] s = {"zero", "one", "two", "three", "four", "five"};  var x =  s .Select((a,i) =&gt; new {Value = a, Index = i}) .Where(b =&gt; b.Value.StartsWith("t")) .Select(c =&gt; c.Index);   i.e. I'm looking for a more efficient or more elegant way to get the positions of the items matching the criteria. "Taste" is to "flavor" as "touch" and "sight" are to what? For the senses, we have:    flavor for taste aroma/odor/scent for smell sound for hearing ____? for touch/feel ____? for sight/see   So one tastes a flavor, smells an aroma, hears a sound, feels a(n) _____, and sees a(n) _____. For the former, part of me wants to say texture, but I feel that is too specific; for the latter, I want to use visual or sight, but but does that make sense, seeing a visual or a sight? Convolution is uniformly continuous and bounded Suppose $f\in L^\infty(\mathbb{R})$ and $K\in L^1(\mathbb{R})$ with $\int_\mathbb{R}K(x)dx=1$. Show that the convolution $f\ast K$ is a uniformly continuous and bounded function.  The definition of the convolution is $(f\ast K)(x)=\int_\mathbb{R}f(x-y)K(y)dy$.   There is the inequality $\|f\ast K\|_\infty\leq\|f\|_\infty\|K\|_1$, which yields that $f\ast K$ is bounded. But what about uniform continuity? Multiple outputs for beamer handouts I'm currently generating some presentations with beamer for students of my course. Some like to print the material, so I created a handout. Some students prefer to have 2,3,4,6 etc. pages per sheet of A4 paper. How can I go about to automatize the following code, so that it outputs 4 different files in 1x2,1x3,2x2,2x3 format?  I'd like to avoid having to compile it again everytime for the different formats.  \documentclass[a4paper]{article} \usepackage{pdfpages}  \begin{document} \includepdf[pages=1-last,nup=1x2,landscape=false,frame=true,             noautoscale=false,scale=1,delta=0mm 5mm]{Pres7Chap13-Handout.pdf} \end{document} Are all oscillatory motions periodic motions? For example, if a pendulum system in the real world oscillates its amplitude and period will eventually decrease. Does that still count as a periodic motion? Since the motion doesn't have the same amplitude at equal time periods. Which is the correct sentence, if there is a correct one?     I use to be a hitman.        I used to be a hitman.   I've read the second sentence recently in a book, but I was sure it should be I use to be a hitman. of a monic polynomial $f \in \mathbb F\left[x\right]$ in $1$ variable $x$ over a field $\mathbb F$ plays an important role in understanding the structure of finite dimensional $\mathbb F[x]$-modules.  It is an important fact that the characteristic polynomial and the minimal polynomial of $C(f)$ are both equal to $f$. This can be seen quite easily by induction on the degree of $f$.  Does anyone know a different proof of this fact? I would love to see a graph theoretic proof or a non inductive algebraic proof, but I would be happy with anything that makes it seem like more than a coincidence! I've had my Trek 3900 for about a year now, and I replaced the chain about 3 months ago, but otherwise it's running with the same parts it came with (not counting tubes and tires).  I had to replace my chain because it had gotten really rusty from riding in rain/mud/water on trails, and had started skipping.    My problem is, whenever I ride, if I get above or below a very light pressure when pedaling, the chain skips. I was wondering if this could be caused by my chain, which has gotten a little rusty but not as stretched as the other one was, or if I might need a new cassette?    I just readjusted my derailer, but it still skips.   Does anybody know what could be causing this? Posting and answering questions you have already found the answer to Sometimes you spend a day or more solving a technical problem, and when you finally solve it, you may want to post it on your blog (if you have one) to share with the community.  However, most developers don't have a lot of time to update their blogs, and that is why personal blogs are not ranked very highly on Google/Bing.  So even if you describe a brilliant idea, chances are that, except a few of your friends, nobody will ever find it. This is a common reason why some developers start their blogs and soon give up; it is not interesting to write for the community if you have no feedback on your posts.  Unlike personal blogs, Stack Exchange sites are highly ranked in Google (I was amazed when I saw that a question asked on SO just an hour ago appeared 3rd in my Google search!), so if your question and answer are valuable for others, they will be rated highly and will be visible for other developers.  With this in mind, is it good practice to post a question and answer it yourself immediately when you want to share an idea with the community? Product Notation for Multiplication in Reverse Order Is there a standard notation for multiplication in reverse order? For example consider the problem  $$x_{k+1} = A_k x_k$$  where $x_i \in \mathbb{R}^n$ and $A_i \in M_n(\mathbb{R})$, ($i=0,1,2,\dots$) without any further assumptions on $A_i$. The solution to this problem is  $$x_k = A_{k-1} \dots A_1 A_0 x_0$$  Obviously, writing  $$x_k = \prod_{i=0}^{k-1} A_i x_0$$  is wrong because of the multiplication order. But I'm also unconfortable to use  $$x_k = \prod_{i=k-1}^{0} A_i x_0$$  as the notation suggests that we need to increment $i$, not decrement it. Also, one may need to write $\prod_{i=k}^{m} A_i$. Then, we need to explicitly state $m &lt; k$ to imply ordering.  I can always write the open form but as similar products frequently occur in calculations in my work I want to express them in a more compact way. The question is, is there a standard and nice notation to do so? There are some suggestions in , but I think none of them are "nice enough" to work with.  I came up with the notation  $$x_k = \coprod_{i=k-1}^{0} A_i x_0$$  to imply decrementing $i$ rather than increment it, but I don't know if it is used in somewhere else or there is a standard notation. How do you find all subclasses of a given class in Java? How does one go about and try to find all subclasses of a given class (or all implementors of a given interface) in Java? As of now, I have a method to do this, but I find it quite inefficient (to say the least). The method is:    Get a list of all class names that exist on the class path Load each class and test to see if it is a subclass or implementor of the desired class or interface   In Eclipse, there is a nice feature called the Type Hierarchy that manages to show this quite efficiently. How does one go about and do it programmatically? is it safe to keep database connections open for long time I have a .net client application which is connected to a remote database. Is it safe to keep a single connection open for the lifetime of the client (hours)? Does the answer hold if I have multiple (10 or 100) clients running? Can Mjolnir "stick" to anything? I've been interested in non-standard analysis recently. I was reading up on it and noticed the following interesting comment on the , right after giving an example of a nonstandard differentiation:     The use of the standard part in the definition of the derivative is a rigorous alternative to the traditional practice of neglecting the square of an infinitesimal quantity... the typical method from Newton through the 19th century would have been simply to discard the $dx^2$ term.   I've never heard anything like this before, and really find it fascinating that Newton's method was to define the relation $dx^2 = 0$. If we actually formalize the above structure by taking $\mathbb{R}$ and adjoining an element $dx^2 = 0$ to it, we get the "dual numbers," isomorphic to the quotient ring $\mathbb{R}[x]/x^2$. I'd seen some things about how this algebra plays into automated differentiation algorithms for some computer software systems, but I've never heard anything about Newton directly working in this algebra. So I have a few questions:   Does anyone have more historical information on the way that Newton performed differentiation, and its relation to the dual numbers? Does anyone know how effectively real analysis can be formalized with the dual numbers? Does the resulting system play nice enough to develop all of the important modern results? If we start with $\mathbb{C}[x]/x^2$ instead, can we likewise develop complex analysis?   Since this idea is so simple, I'm very curious how powerful it is. I'm also curious if it has any major drawbacks too, since I'm not sure why anyone would mess with the foundational baggage involved in defining the hyperreals if this simple 2-dimensional real algebra could really do the trick. Inaccurate shading on object I am relatively new to Blender so please excuse me if this is rather amateur!   The bottom of my torus has poor surface quality, I have scaled the vertices down for a smaller (variable) tubular radius all the way around the torus and at the bottom the surface quality is awful, with inaccurate shading. Any ideas as to what is wrong and/or how I could fix this?  Thanks, itsanate